In an isosceles triangle, the sides and the

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1 51 LSSON Properties of Isosceles and quilateral Triangles Warm Up New oncepts Math Reasoning nalyze oes Theorem 51-1 also apply to equilateral triangles? How do you know? 1. Vocabulary triangle with two congruent sides is a(n).. In RST, R S and m T = 80. etermine m R. (13) (18) 3. Multiple hoice Which statement is always true? (13) If a triangle is isosceles, then it is equilateral. If a triangle is equilateral, then it is isosceles. oth and. Neither nor. In an isosceles triangle, the sides and the angles of the triangle are classified by their position in relation to the triangle s congruent sides. leg of an isosceles triangle is one of the two congruent sides of the triangle. In the diagram, and are the legs. The verte angle of an isosceles triangle is the angle formed by the legs of the triangle. The verte angle is. The base of an isosceles triangle is the side opposite the verte angle. The base of is. base angle of an isosceles triangle is one of the two angles that have the base of the triangle as a side. In, and are base angles. Theorem 51-1: Isosceles Triangle Theorem If a triangle is isosceles, then its base angles are congruent. LMN is isosceles. Therefore, M N. L M N orollary If a triangle is equilateral, then it is equiangular. Online onnection ample 1 Proving the Isosceles Triangle Theorem Prove the Isosceles Triangle Theorem. Given: is an isosceles triangle with. is the midpoint of. Prove: 336 Saon Geometry

2 Statements Reasons 1. is isosceles 1. Given.. efinition of isosceles triangle 3. = 3. efinition of midpoint. 5.. efinition of congruent segments 5. Refleive Property SSS Triangle ongruence Postulate PT The onverse of the Isosceles Triangle Theorem is also true, as is the onverse of orollary Theorem 51-: onverse of the Isosceles Triangle Theorem If two angles of a triangle are congruent, then the sides opposite those angles are also congruent. orollary If a triangle is equiangular, then it is equilateral. Hint If you are not sure which side of the triangle is the base and which sides are the legs, sketch a triangle and label the angles and sides with as much information as possible. ample Using the Isosceles Triangle Theorem and Its onverse a. Triangle F is isosceles, and its verte angle is at. If m = 36, determine m and m F. The base angles of F are and, so by the Isosceles Triangle Theorem, F. y the definition of congruent angles, m F = m, so they each measure 36. Therefore, m + m + m F = 180 Triangle ngle Sum Theorem 36 + m + 36 = 180 Substitute m = 108 Solve b. The perimeter of GHJ is 1 inches, and G H. If GH = 5 inches, find GJ. y the onverse of the Isosceles Triangle Theorem, GJ HJ. Since the perimeter is 8 inches and GH = 5 inches, P = GH + HJ + GJ Formula for perimeter 1 = 5 + HJ + GJ Substitute. 1 = 5 + GJ + GJ efinition of congruent segments 1 = 5 + GJ Simplify. GJ = 3.5 in. Solve. Lesson

3 ample 3 Using Relationships in quilateral Triangles triangle is equiangular and has a perimeter of.5 centimeters. etermine the length of each side. y orollary 51--1, the triangle is equilateral. Let the length of each side be s. The perimeter is the sum of the three sides. P = s + s + s Formula for perimeter.5 = 3s Substitute and simplify. s = 7.5 cm Solve. Math Reasoning onnect How are Theorems 51-3 and 51- related to each other as conditional statements? Theorem 51-3 If a line bisects the verte angle of an isosceles triangle, then it is the perpendicular bisector of the base. Theorem 51- If a line is the perpendicular bisector of the base of an isosceles triangle, then it bisects the verte angle. The diagram illustrates both of these theorems. The altitude TU bisects the verte angle and is a perpendicular bisector of the base of the triangle. T ample Proving Theorems 51-3 and 51- a. Prove Theorem Given: is isosceles, bisects Prove: is the perpendicular bisector of Statements Reasons 1. is isosceles, 1. Given bisects.. efinition of angle bisector efinition of isosceles triangle.. Refleive Property SS Triangle ongruence Postulate PT 7. = 7. efinition of congruent segments PT 9. and form adjacent 9. efinition of adjacent angles angles If lines form congruent adjacent angles, they are perpendicular 11. is bisector of 11. efinition of perpendicular bisector U 338 Saon Geometry

4 b. Write a paragraph proof of Theorem 51-. Given: is isosceles, is the perpendicular bisector of Prove: bisects Since is isosceles,. y the Refleive Property,. oth and are right triangles, since is the perpendicular bisector of and forms two right angles at. Therefore, by the Hypotenuse-Leg Right Triangle ongruence Theorem. y PT,. Therefore, by the definition of an angle bisector, bisects. Math Reasoning Model Picture the telephone pole with cables securing it to the ground from each side. re the cables all coplanar? re any two of them coplanar? ample 5 pplication: Infrastructure This figure shows the north and east view of a telephone pole that is secured by four cables of equal length. a. plain why the base angles, PQ and PRQ, are congruent. In PR, the cable lengths P and RP are equal, so P RP by the definition of congruent segments. Therefore, PR is isosceles by definition. pplying the Isosceles Triangle Theorem, the base angles of PR are congruent, so PQ PRQ. P Q North View P Q ast View R b. Prove that these angles are also congruent to the base angles and. y the Refleive Property of ongruence, PQ PQ. It is given in the problem that P P, so by the Hypotenuse-Leg Right Triangle ongruence Theorem, PQ PQ. y PT,. Since P is isosceles, by the Isosceles Triangle Theorem. It is given that R, so by the Transitive Property of ongruence, R. Lesson Practice ( ) ( ) ( ) ( 3) a. For the isosceles triangle shown, determine the missing angle measures. b. The perimeter of XYZ is 15. centimeters, and X Z. If XY = 6.3 centimeters, determine XZ. 7 c. If the verte angle of an isosceles triangle measures 0, what are the measures of each of its base angles? d. triangle is equiangular and its perimeter is 7 feet. etermine the length of each side. Lesson

5 ( 5) e. ngineering This diagram shows the side-view profile of a bridge. etermine the angle that each half of the bridge makes with the horizontal. 150 ft ft Practice istributed and Integrated 1. In FGHJ, m H < m FJG, GH = - 1, and FG = + 8. Find the range of values for. (Inv ) F G. From the statement, If Fabian s socks are clean, then they are in the dresser, what can you conclude about what will happen when Fabian s socks are clean? (1) J H 3. a. etermine this figure s perimeter. b. etermine its area. (0) 8 in. 15 in. 16 in. *. Write plain how you would find the geometric mean (50) of and 7. 1 in. 17 in. y (Inv 3) 5. What is the measure of each eterior angle in a regular heagon? 6. Using the diagram, find the length of to the nearest hundredth (35) of a centimeter. * 7. In PQR, PR QR and m R = 118. (51) a. Identify the verte angle. b. etermine m P. y (9) 8. lgebra polyhedron has 10 more edges than vertices. How many faces does the polyhedron have? 6 cm 9. Find the unknown length of the side in the triangle shown. (9) * 10. Write plain why each angle of an equilateral triangle measures 60. (51) 13 m 1 m 11. rt In order to design part of her tile pattern correctly, Teresa (3) needs to make the consecutive angles shown supplementary. How can she ensure the angles will be supplementary? y 1. lgebra Two lines are perpendicular. One line has an equation y = 1 m - and the (37) other line has an equation of y = n Find one value for m and n. * 13. onstruction builder needs to position a support brace as shown. (50) What is the length of the support brace, to the nearest tenth? 3 30 Saon Geometry

6 1. Justify plain why, then find. (6) 15. onve pentagon PQRST has vertices P(0, 0), Q(-, ), R(-1, ), S(, y), (5) and T(, ). QR = ST and RS =. Find (, y) Surveying Kristi, a map surveyor, is using an east-west baseline to (18) locate various landmarks. She measures the clockwise angle from the baseline to the line passing through her surveying instrument and the landmark. Kristi takes two sightings from a clock tower, as this diagram shows. a. What measure is the angle between the two sightings? b. What theorem did you use in part a? lock Tower 1 80 aseline 17. In the diagram shown at right, what information is needed (30) to conclude that TUV F? U F 18. Generalize Triangle GHI has vertices G(0, 0) and H(a, b). Find (5) coordinates for a point I so that GHI is a right triangle. T V Use the LL ongruence Theorem to show that OPQ RST. (36) T P S O Q R 0. What is the equation of a line perpendicular to y = - + 1, passing through (37) the origin? 1. ell Phone Towers Three cell phone towers are the vertices of (39) a triangle at right. The measure of M is 10 less than the measure of K. The measure of L is one degree greater than the measure of M. Which two towers are closest together? *. nalyze Give a two-column proof of the onverse of the (51) Isosceles Triangle Theorem. Given: Prove: is isosceles. Hint: rop an altitude from point to the base of. * 3. Find the value of and y on the triangle shown. (50) Tower L *. Multi-Step etermine whether each set of numbers can be the side lengths of a triangle. If they can be a triangle, determine whether it is an acute, obtuse, or right triangle. a. 99, 3 13, 1 b. 7, 8, 3 c. 8, 7, 1 (33, 39) Tower M Tower K y Lesson 51 31

7 5. etermine the perimeter and area of this figure. Give eact answers. (0) 5 in. 10 in If KLM F, what side of F corresponds to side KM? (5) 7. Using the diagram, find PY in terms of if PV = 3 and YU =. Point P is the (38) incenter of the triangle. T Y P U X V Z 8. Multiple hoice The intercepted arc of an inscribed angle is a semicircle (7) if and only if the measure of the angle is * 9. Find the value of in this figure. (51) 6 - _ Prove Theorem 39-: If one angle of a triangle is larger than another Q (8) angle, then the side opposite the first angle is longer than the side opposite the second angle. Given: m P > m R Prove: QR > QP Hint: There are two cases you must consider. One where QR < QP and one where QR = QP. P R 3 Saon Geometry

8 5 LSSON Properties of Rectangles, Rhombuses, and Squares Warm Up 1. Find the area of the regular quadrilateral. lassify this quadrilateral. (15). Vocabulary quadrilateral with two pairs of parallel sides is a. 3. Find the perimeter of this composite figure. Then, name each quadrilateral in the figure. (19) (0) 1.5 cm 8.7 m New oncepts The diagonals of parallelograms have special properties. Recall that a rhombus is a parallelogram with four congruent sides, a rectangle is a parallelogram with four right angles, and a square shares the properties of both a rectangle and a rhombus. One property of the diagonals of a parallelogram has already been introduced: they bisect each other. Three more are introduced in this lesson. Properties of a Rectangle: ongruent iagonals Math Reasoning nalyze re the diagonals of a square congruent? How do you know? The diagonals of a rectangle are congruent. P Q PR QS If a quadrilateral is a parallelogram, it is a rectangle if and only if the above property is true. S R ample 1 Using iagonals of a Rectangle Online onnection rectangular barn door has diagonal braces. If is 6 feet, what is the length of? = = 6 = 1 = 1 iagonals of a rectangle are congruent iagonals of a parallelogram bisect each other Substitute. Segment ddition Postulate efinition of segment congruence Lesson 5 33

9 ploration Using ontruction Techniques to raw a Rhombus In this eploration, you will use simple construction techniques to construct a quadrilateral, then classify it. You may wish to review onstruction Lab 1 before this eploration. 1. raw JK. Set your compass to JK. Place the compass point at J and draw an arc above JK L. hoose and label a point L on the arc. What is the relationship between JK and JL?. Place the compass point at L and draw an arc to the right of L. L J K 3. Place the compass point at K and draw an arc that intersects the arc you drew in step. Label the point of intersection M. How are JK, KM, ML, and LJ related?. How do you know that the quadrilateral you have L drawn is a rhombus? 5. raw the diagonals JM and LK and label their point of intersection P. Measure LPM. What can you determine about the diagonals? J K 6. y measuring angles, determine the relationship between the diagonals and the angles of the rhombus. J K M Math Language Model Sketch a trapezoid and a kite. oes it seem like either figure has perpendicular diagonals? Properties of a Rhombus: Perpendicular iagonals The diagonals of a rhombus are perpendicular. H K HJ IK I J If a quadrilateral is a parallelogram, it is a rhombus if and only if the above property is true. Since a square is both a rhombus and a rectangle, its diagonals are both perpendicular and congruent. Properties of a Rhombus: iagonals as ngle isectors ach diagonal of a rhombus bisects opposite angles. ecause opposite angles of a rhombus are equal, when they are bisected by a diagonal, four congruent angles result , and If a quadrilateral is a parallelogram, it is a rhombus if and only if the above property is true. 3 Saon Geometry

10 ample Using Properties of iagonals of a Rhombus F is a rhombus. Find the measure of each angle. a. m Since m is 90, then we know that m + m = 90 (3 + 1) + ( + 10) = 90 Substitute. + = 90 Simplify. = 17 Solve. Now substitute the value of to find the measure of. m = m = 3(17) + 1 Substitute for. m = 63 Simplify. b. m Since the diagonals of a rhombus bisect the angles, m = m. m = + 10 m = m = 7 F (3 + 1) ( + 10) Hint It may be possible to classify a parallelogram using more than one of the properties in this lesson. ample 3 Using Properties of Parallelograms UVWX is a parallelogram. ecide what type of parallelogram it is by using the properties of rectangles and rhombuses. a. etermine whether the diagonals are congruent and classify the parallelogram. UW = ( -1-6) + ( - 1) = 58 VX = (1 - ) + (-1-6) = 58 Since UW = VX, then the diagonals are congruent. y the ongruent iagonals Property of a Rectangle, the shape must be a rectangle. U 6 O y V X 6 W b. etermine whether the diagonals are perpendicular and classify the parallelogram. slope of UW = _ = - 3_ slope of VX = _ = _ 7 3 Since - 3_ 7 _ 7 = -1, UW is perpendicular to VX. 3 This implies that the parallelogram is a rhombus. Since the shape is both a rectangle and a rhombus, it is also a square. Lesson 5 35

11 ample pplication: rchitecture rectangular building is designed with steel support braces placed diagonally in the interior. etermine the length of the steel brace that will be used for diagonal. a + b = c = c c = 130 ft F = 130 ft F = 130 ft Pythagorean Theorem Substitute Solve Substitute iagonals of a rectangle are congruent Substitute 50 ft 10 ft F Lesson Practice a. In rectangle MNOP, MO = 5. inches. What is the length of NP? ( 1) WXYZ is a rhombus. Using the diagram, answer the questions that follow. b. Find m OXY. X W ( ) (6-1) c. Find m OYZ. ( ) O Z ( + ) Y d. Quadrilateral RSTU has a center point, V. If RT SU, and RT SU, ( 3) classify the quadrilateral. e. rchitecture building is made with a rhombus-shaped courtyard. If the longer diagonal walkway is 50 feet and the shorter one is 0 feet, what is the perimeter of the courtyard to the nearest foot? ( ) Practice istributed and Integrated 1. raw a net for this polyhedron. (Inv 5). Multi-Step Find the orthocenter of JKL with vertices J(3, 6), K(3, -9), and L(-5, -5). (3) 3. Write ompare a regular octagonal prism and a cylinder. onsider what happens as the number of sides of the base of a prism increases. (9). arpentry cabinetmaker needs to position a support brace as shown. What is the length of the support brace? 7 (50) * 5. rt Joni wants to use a square piece of paper for an art project. (5) plain how she could easily determine if a piece of paper is square. 36 Saon Geometry

12 6. The circumference of a circle is 113 feet. If a sector has an area of 1 ft, what is the measure of the arc to the nearest degree? (35) 7. rror nalysis Henrietta is trying to find the slope of the line that passes through the point (8, 0) and is perpendicular to the line y = + 1. Her answer is y = 1 +. Is she correct? Why or why not? (37) 8. re these two triangles similar? Give a reason to support your answer. (6) P 8 Q 16 U R 0 T 10 S 9. Generalize plain how a parallelogram could be similar to a rectangle. (1) y * 10. lgebra rhombus has two angles that each measure (5) (9 + 1) and two angles that each measure (0 + 5). Find the measure of each of the four angles in the rhombus. * 11. Find the geometric mean of 11 and 5. (50) * 1. hemistry This diagram shows the atoms and bonds in a water molecule. The (51) bond angle at the oygen (O) atom is always The distances from the oygen atom to each hydrogen (H) atom are equal. What are the measures of the other two angles, to the nearest tenth? H O?? H 13. Multiple hoice Which statement has a false converse? (10) If two angles are supplementary, then they sum to 180. If a triangle has two congruent angles, then it is isosceles. If a number is an even prime, then the number is. If two angles are complementary, then they are both acute. 1. nalyze For a triangle with vertices L(0, 0), M(6, 0), and N(3, y) to be equilateral, (5) what must be the value of y? * 15. Multi-Step The vertices of a square KLMN are K(0, 1), L(, -), M(1, -6) and (5) N(-3, -3). Show that the diagonals are congruent perpendicular bisectors of each other. 16. If a circle has a circumference of 6, and an arc in that circle has a length of, (35) what is the angle measure of the associated sector? y (7) y 17. lgebra In the circle shown, find the measure of I. H 18. In isosceles triangle PQR, PQ = 8, QR = 8, and m Q = 86. (51) a. Identify the verte angle. b. etermine m R. 19. What is the relationship between angles intercepted by the same (7) arc? I 5m 8m 10m F G * 0. Write a paragraph proof showing that if one side of a triangle (31) is longer than another side, then the angle opposite the first side is larger than the angle opposite the second side. Given: RS > RQ Prove: m RQS > m S Q R P S Lesson 5 37

13 1. In isosceles triangle, and each base angle measures 0. (51) etermine m. y. lgebra Write an inequality to show the largest value for that (33) makes the triangle obtuse if the longest side is 9 units In a right triangle, one leg is 36 feet long, and the hypotenuse is (9) 39 feet long. What is the length of the third side? 9 *. Fence onstruction homeowner wants to build a fence gate with reinforcing (5) diagonal braces. How can he make sure the gate is rectangular without measuring the angles? * 5. Predict This figure is formed from three congruent rectangles. (0) a. etermine the perimeter of the figure. b. onsider the figure formed by etending the pattern to four congruent rectangles. etermine the perimeter of the new figure. c. etermine a formula for the perimeter of a figure in the same pattern formed from n congruent rectangles. 3 cm cm 1 cm 1 cm 6. To measure the distance F across the lake, a surveyor at S locates (6) points, F, G, and H as shown. What is the length of F? 7. Write escribe how to circumscribe a circle around an obtuse triangle. (38) 8. is a parallelogram. If is 3 times longer than and the (3) perimeter of is 1, how long is each side? 9. Suppose you are to prove. State the assumption you would (8) make to start an indirect proof. * 30. Hiking Yvette was planning on going around a thick, circular clump of trees, (3) but she found a shortcut through it. If the diameter of the circular area is 100 meters, how much shorter is her direct path, to the nearest meter, than traveling around the trees? F 30 feet G feet 0 feet S 6 feet H 3.5 feet 38 Saon Geometry

14 53 LSSON Right Triangles Warm Up 1. Vocabulary The name given to a triangle with one 90º angle is. (13). Find the area of a right triangle with legs that are 11 inches and 17 inches long. (18) 3. right triangle has legs that are 8 units and units long. What is the ratio of the triangle s hypotenuse to its shortest leg? (9) New oncepts Some right triangles are used so frequently that it is helpful to remember some of their particular properties. These triangles are called special right triangles. The two most common special right triangles are the triangle and the triangle. Since the triangle has two angles with equal measures, it is also an isosceles right triangle. Properties of a Triangle: Side Lengths In a right triangle, both legs are congruent and the length of the hypotenuse is the length of a leg multiplied by. Hint The name of each special right triangle gives the measure of its angles triangles are often used because they are one half of a square. aution When the denominator of a fraction has a square root in it, it must be rationalized. In this eample, multiplying both the top and bottom of the fraction by eliminates the root in the denominator. 5 5 ample 1 Finding the Side Lengths in a Triangle a. Use the properties of a right triangle to find the length of the hypotenuse of the triangle. The length of the hypotenuse is equal to the length of a leg times. Since the leg is inches long, the hypotenuse has a length of inches. b. Use the properties of a right triangle to find the length of a leg of the triangle. The length of the hypotenuse is equal to the length of the leg times. To find the length of a leg when given the hypotenuse, divide by instead. The length of a leg of the triangle is 3 = 3 feet. 5 3 ft 5 in. Lesson 53 39

15 ample Finding the Perimeter of a Triangle with Unknown Measures Find the perimeter of the triangle. 1 yd 5 The length of the hypotenuse is equal to the length of the leg times. Therefore, the hypotenuse is 1 yards long. The perimeter can be found by adding the lengths of the three sides together. P = P = + 1 P 0.97 Therefore, the perimeter is approimately 1 yards. Though it is often faster to use the properties of triangles to find unknown lengths, the Pythagorean Theorem can still be used to determine lengths in special right triangles. ample 3 pplying the Pythagorean Theorem with Right Triangles Find the length of the missing sides to the nearest foot, using the Pythagorean Theorem ft Math Reasoning Verify Use the properties of triangles to find. Is the result the same? Since the legs are congruent, let represent the length of the legs of the triangle. Therefore, a + b = c + = 15 = 1565 = _ 1565 = Therefore, the missing side length is approimately 88 feet. Online onnection Saon Geometry

16 ample pplication: Park onstruction square park is to be fenced around the perimeter with a snow fence for an upcoming outdoor concert. There is a diagonal path that is 30 feet long through the park. How much snow fence is required? Use the -Step Problem-Solving Process. Hint good way to check your work is to consider the possible bounds (minimum and maimum) the answer could have. oes your answer fall between the bounds of the minimum and maimum? In this case, any answer over 170 feet or under 0 feet would clearly be incorrect. Understand The fence is to be placed around the perimeter, so the perimeter must be found. The diagonal of the square is given. diagram would be a helpful visual aid to understand this problem. Plan First, draw a diagram. Identify the lengths that need to be found and use the properties of triangles to solve for them. dd the length of each side together to find the perimeter. Solve This involves finding the length of the legs of the triangle created by two adjacent sides of the park and the diagonal path. Path 30 = _ 30 = 30 = Therefore, the length of the side of the square park is 15 feet. To find the perimeter of the park, the formula for the perimeter of a square will be used. P = l P = (15 ) P = 860 P 116. Therefore, the perimeter of the park, and thus the amount of fencing needed, is approimately 116 feet. heck Here, since the diagonal is longer than a side, each side must be less than 30 feet. So the perimeter must be less than 30, or 170 feet. The answer of 116 feet seems to make sense because it is less than 170 feet. 5 Lesson Practice ( 1) ( 1) a. Find the length of this triangle s hypotenuse. b. Find the length of this triangle s missing side. 63 m 5 31 yd 5 Lesson

17 ( ) ( 3) ( ) c. Find the perimeter of the triangle, to the nearest tenth of an inch. d. Find the length of the missing sides to the nearest mile. e. square building has a diagonal length of 150 feet. What would be the square footage of one floor of the building? 5 18 in. 5 8 mi Practice istributed and Integrated 1. onstruction The measurements in the diagram are from the attic space in a new home. If the angle measure of 7 is an inaccurate label on the diagram, what is the range of degrees that the mislabeled angle could be? It is given that the side opposite the mislabeled angle is the longest side of the triangle, and the side opposite the 8 is the shortest side. (39) 5.5 ft 7 7 ft 8. figure has 1 congruent edges and 8 vertices. lassify the figure. (9) b * 3. Find the eact value of the length of leg a in the triangle. (53). enter of Gravity re the orthocenter and the centroid both centers of gravity? If not, which one is? (3) a 5 5 cm * 5. Is the following statement always, sometimes, or never true? (5) parallelogram is a rectangle. T 6. Find the value of and y in the figure at right to the nearest tenth. (50) 7. composite figure is formed by a rectangle with a square removed at one corner. The rectangle measures 6 1 inches by 5 inches. The removed square has side lengths of 3 1 inches. a. etermine the perimeter of the figure. b. etermine the area of the figure. (0) 7 5 y * 8. Write Is every right isosceles triangle a triangle? plain. (53) 9. Identify each line or segment that intersects the circle shown. (3) L y * 10. lgebra The value of the side length in a triangle is inches. (53) What would be the algebraic epression for the length of the triangle s hypotenuse? 11. Write a similarity statement to eplain why the two (6) triangles shown are similar. 100 N M K Saon Geometry

18 1. nalyze What information must be known about two similar triangles in order to () find the ratio of their perimeters? * 13. nalyze Write a flowchart proof showing that if a triangle is equilateral, then (51) it is equiangular. 1. What is the total area of the shaded sectors if the diameter of the circle is (35) 8 meters? Write your answer in terms of π. 15. Find the distance from (-5, ) to the line = 13. () y 16. lgebra If in, = (1 + 11), m = 1, m = 1, and (30) = 7 units, and in F, = (5 + 18), m F = 1, m F = 1, and F = 7 units, what is the value of? 17. Justify Give a possible value for the length of XY. plain your answer. 18. What is the value of b in the proportion _ 5 = _ 7 b? (1) (Inv ) X Y H Z G I 19. rt n artist is making a round ceramic plate with a pattern of lines on it. (7) If m KLM = 0, and m MP = 30, find m KNP. 0. Suppose a chord of a circle is 10 inches long, and the radius of the circle is (3) also 10 inches. What is the measure from the chord to the center of the circle? N L * 1. Multiple hoice What would be the perimeter of a triangle with a (53) hypotenuse of 73 feet, to the nearest foot? 5 feet 176 feet 10 feet 198 feet K M P. esign gift bo has the net shown in this figure. Use the net to provide a countereample to the following statement. (1, Inv 5) If the net of a three-dimensional figure has all lateral faces congruent, then the figure is closed. * 3. WXYZ is the rectangle shown. Find XY. (5). Multi-Step Find the centroid of F with vertices (-3, ), (3) (9, 8), and F(3, -). W 10. in. 1.6 in. O X 5. It is given that F. If is 3 units, is 1 units, (1) and is 11 units, what is the length of F? Z Y 6. If two sides of one triangle are proportional to two sides of another triangle, (6) and if their corresponding included angles are congruent to each other, then the triangles are similar by. Lesson

19 * 7. Find the eact value of the length of the hypotenuse in the triangle. (53) 16 yd 5 8. Use the Hypotenuse-ngle ongruence Theorem to prove that F. (36) F * 9. Write plain why the following statement is true. (5) If a quadrilateral is a square, then it is a rhombus. * 30. Surveying Renée takes the bearings of landmarks at,, and from the same (51) position,. Landmark earing from : hurch Steeple 3 : lock Tower : Water Tower Suppose Renée chose point to be equidistant from the church steeple and the water tower. What must be true about the clock tower s distance from each of the other two landmarks? Why? 35 Saon Geometry

20 5 LSSON Representing Solids Warm Up 1. Vocabulary prism with si square faces is called a.. Name each of the pictured solids. If the solid is a prism or pyramid, classify it. 3. ccording to uler s Formula, if a polyhedron has 7 faces and 10 vertices, how many edges does it have? (9) (9) (9) New oncepts In a perspective drawing, nonvertical parallel lines appear to meet at a point called a vanishing point. If you look straight down a highway, it appears that the edges of the highway eventually come together at a vanishing point, Math Language The vanishing point is the point in a perspective drawing on the horizon where parallel lines appear to meet. like point in the diagram. In a perspective drawing, the horizon is the horizontal line that contains the vanishing point(s). drawing with just one vanishing point is called one-point perspective. ample 1 rawing in One-Point Perspective raw a rectangular prism in one-point perspective. Use a pencil with an eraser. Step 1 raw a square and a horizontal line above it representing the horizon. Mark a vanishing point on the horizon. Step raw a dashed line from the vanishing point to each of the four corners of the square. Step 3 Using the dashed lines drawn in Step, draw the sides of a smaller square. Online onnection Step onnect the two squares and erase the reference lines and the horizon that are located behind the prism. This prism is drawn from a one-point perspective. Lesson 5 355

21 drawing with two vanishing points is said to have two-point perspective. Look at the following eample to see how a drawing can be made from a two-point perspective. ample rawing in Two-Point Perspective raw a rectangular prism in two-point perspective in which the vanishing points are above the prism. Math Reasoning Model ould you also make a two-point perspective drawing by placing the vanishing points below the original line segment? Step 1 raw a horizontal line that represents the horizon. Place two vanishing points on the horizon. raw a vertical line segment below the horizontal line and between the two vanishing points, representing the front edge of the prism. Step raw dashed lines from each vanishing point to the top and bottom of the vertical line as shown. Step 3 raw vertical segments between the dashed lines from Step as shown and draw segments to connect them to the first segment. Step raw dashed perspective lines from the segments drawn in Step 3 to each of the vanishing points as shown. Step 5 raw a dashed vertical line between the two intersections of the perspective lines just drawn. Sketch the segments that make the top of the prism. Step 6 rase the horizon line and the dashed perspective lines. Keep the dashed lines inside the prism that represent the edges that are hidden. This prism is drawn from a two-point perspective. n isometric drawing is a way of drawing a three-dimensional figure using isometric dot paper, which has equally spaced dots in a repeating triangular pattern. The drawings can be made by using three aes that intersect to form 10 angles, as shown in the diagram Saon Geometry

22 ample 3 reating Isometric rawings reate an isometric drawing of a rectangular prism. raw the three aes on the isometric dot paper as shown above. Use this verte as the bottom corner of the prism. raw the bo so that the edges of the prism run parallel to the three aes. Shading the top, front, and side of the prism will add the perception of depth. In a two-point perspective drawing, it appears that one edge of the solid is the front of the diagram. In a one-point perspective drawing, it appears that a face of the solid is the front. ample pplication: rafting Hint n architecture firm is planning to construct a rectangular building on a corner lot. The client would like a drawing that shows the building as though someone is looking at it from one edge. Should the drawing be from a one-point or two-point perspective? Make a sketch of what the drawing should look like. Since the front of the drawing will be an edge of the building, a two-point perspective drawing is appropriate. The diagram shows a completed view of the building. Lesson Practice ( 1) ( ) ( 3) ( ) a. raw a rectangular prism in one-point perspective in which the vanishing point is to the left of the square. b. raw a cube in two-point perspective with the vanishing points and horizon below the vertical line. c. Make an isometric drawing of a triangular prism. d. rafting Morgan wants to make a wooden bookshelf with two shelves. The bookshelf will be 1 meter wide, 1 meter deep, and 1.5 meters tall. To decide how much wood to buy, Morgan will draw his plans for the bookshelf. Should the drawing be from a one-point or two-point perspective? Sketch what Morgan s drawing should look like. Lesson 5 357

23 Practice istributed and Integrated * 1. raw a triangular prism in one-point perspective so that the vanishing point is (5) below the prism.. Write plain why the following statement is true. If a quadrilateral is a square, then it is a rectangle. (5) y (3) y 3. lgebra Find the length of ZP in the diagram.. What is the shortest distance from (5, 3) to the line y = - + 8? () Z P Y 11 X 13-3 * 5. rchitecture n architect is creating different perspective drawings for a new (5) building. The building is a rectangular prism and the client would like a drawing that focuses on the front façade of the building. Should the architect create the drawing using a one-point or two-point perspective? Sketch a sample drawing of the building. 6. figure has a heagonal base and triangular lateral faces. lassify the figure. (9) 7. Multi-Step Graph the line and find the slope of the line that passes through the points L(, 1) and M(3, -1). Then find a perpendicular line that passes through point N(-, -). (37) 8. Find the value of and y in the triangle shown to the nearest tenth. (50) 13 y 9. What is the sum of the eterior angles of a conve 13-sided polygon? (Inv 3) Is the following statement always, sometimes, or never true? (5) parallelogram is a rectangle. * 11. Trace the figure at right on your paper. Then locate the (5) vanishing point and the horizon line. y 1. lgebra In, m = 90, = (3-7), and (30) m = 60, and in F, m F = 90, = (5-17), and m F = 60. What value of will make F? 13. The point where three or more lines intersect is the. (3) * 1. Use the Hypotenuse-ngle ongruence Theorem to prove (36) that RST UVW. * 15. Find the eact length of the hypotenuse of a right (53) triangle with a leg that is 57 feet long. S R T V U W 358 Saon Geometry

24 16. Formulate Four congruent circles are cut out of a square as shown. Write an (0) epression for the area of the shaded region in terms of the radius of each circle, r. r 17. viation Four jet aircraft are flying in a triangular formation. Jets,, and (51) form a line perpendicular to the flight heading, while jet is midway between the other two. Jet flies directly in front of jet. If m = 37, what does the verte angle of the triangular formation measure? Which theorem did you use? * 18. Use an indirect proof to prove that if two altitudes, X and Y of are (8) congruent, then the triangle must be isosceles. Given: X Y, X and Y are altitudes. Prove: isosceles. * 19. Find the area, to the nearest hundredth, of a right triangle with a (53) hypotenuse of 17 centimeters. y 0. lgebra If a chord perpendicular to a radius cuts the radius in two pieces that are (3) 7 and inches long, respectively, what are the two possible lengths of the chord to the nearest tenth? * 1. Justify How does a two-point perspective differ when the vanishing points are (5) located close together compared with when they are located further apart? Justify your reasoning with drawings.. Find the geometric mean of and 5. (50) 3. Multiple hoice If the diagonals of parallelogram JKLM intersect at P, which of (3) the following is true? JP = LP JP = KP JL = KM JM = KM *. onstruction The support of a shelf forms a right triangle, (53) with the shelf and the wall as the legs. actly how long is this support? shelf ( in.) * 5. nalyze NPQ and STV are similar isosceles triangles. How many () of their si sides do you need numerical values for in order find all the other side lengths and the perimeters of both triangles? plain. wall 5 support Lesson 5 359

25 6. Using the diagram on the right, find the length of MP if OP = 5, (38) NO = 8, and MN = 18. M 7. ycling Katya and Sareema start from the same location and bicycle in opposite directions for miles each. Katya turns to her right 90 and continues for another mile. Sareema turns 5 to her left and continues for another mile. t this point, who is closer to the starting point? (Inv ) 8. rror nalysis arius drew this net of a number cube. plain his error. (Inv 5) N O 1 3 P nalyze Square RSTU has vertices at R(0, ) and S(0, 0). What are the possible (5) coordinates of T and U? 30. esign white triangle with vertices at (0, 0), (, 0), and (0, ) is used to create (11) a logo. blue triangle is added to the design so that its vertices are the midpoints of the sides of the white triangle. The blue triangle divides the white triangle into three smaller white triangles. Smaller blue triangles are placed in each small white triangle so that their vertices are the midpoints of the sides of the small white triangles. 3 y 1 O 1 3 a. Find the coordinates of the vertices of the large blue triangle. b. Find the coordinates of the vertices of each small blue triangle. c. Which of the triangles are congruent, if any? Justify your answer. 360 Saon Geometry

26 55 LSSON Triangle Midsegment Theorem Warm Up 1. Vocabulary Two triangles with congruent corresponding angles and corresponding sides that are proportional in length are. (1) etermine if the triangles in each pair are similar. If they are, state the theorem or postulate that proves it. (6). 3.. New oncepts midsegment of a triangle is a segment that joins the midpoints of two sides of the triangle. very triangle has three midsegments. Math Language The midpoint of a segment is the point that divides a segment into two congruent segments. M The midsegment is always half the length of the side that does not have a midsegment endpoint on it. N P Theorem 55-1: Triangle Midsegment Theorem The segment joining the midpoints of two sides of a triangle is parallel to, and half the length of, the third side. RQ PM and RQ = _ 1 PM M Q N R P Online onnection ample 1 Using the Triangle Midsegment Theorem In the diagram, is a midsegment of. Find the values of and y. y 5 7 From the Triangle Midsegment Theorem, = _ 1, so =. = (7) Therefore, = 1. From the definition of a midsegment, =. So, y = 5. Lesson

27 ample Proving the Triangle Midsegment Theorem Given: is the midpoint of and is the midpoint of. and = _ 1 Prove: Statements Reasons 1. is the midpoint of ; is the midpoint of 1. Given. = ; =. efinition of midpoint 3. + = ; 3. Segment ddition Postulate + =. + = ;. Substitute + = 5. = _ 1 ; = _ 1 5. Solve Refleive Property of ongruence SS Triangle Similarity Theorem efinition of similar polygons If corresponding angles are congruent, lines cut by a transversal are parallel 10. = _ efinition of similar polygons and step 5 Math Reasoning nalyze Is Theorem 55- a conditional statement that is related to 55-1? If so, what is their relationship? Theorem 55- If a line is parallel to one side of a triangle and it contains the midpoint of another side, then it passes through the midpoint of the third side. Since UV RT and RU US, SV VT. R U S V T The measure of QT can be determined using Theorem 55-. Since RU = US in triangle QRS, then U is the midpoint of RS. y Theorem 55-, since TU QS and U is the midpoint of RS, then T is the midpoint of QR. Since T is the midpoint of QR, then QT = TR. The measure of QT is 13 units. R T U 10 Q S 36 Saon Geometry

28 ample 3 Identifying Midpoints of Sides of a Triangle Triangle MNP has vertices M(-, ), N(6, ), and P(, -1). QR is a midsegment of MNP. Find the coordinates of Q and R. R and Q are the midpoints of MN and NP. Use the Midpoint Formula to find the coordinates of Q and R. Q (_ 6 +,_ + (-1) ) = Q (, _ 1 ) R (_ - + 6,_ + ) = R(, 3) M(-, ) y - O - - R P(, -1) N(6, ) Q 6 The midsegment of a triangle creates two triangles that are similar by -Similarity. In the diagram, since, then and. This shows that. midsegment triangle is the triangle formed by the three midsegments of a triangle. Triangle F is a midsegment triangle. Midsegment triangles are similar to the original triangle and to the triangles formed by each midsegment. In the figure, F F F. F ample pplying Similarity to Midsegment Triangles Triangle STU is the midsegment triangle of PQR. a. Show that STU PQR. Hint It may help to sketch the similar triangles separately so they can be compared more easily. Since STU is the midsegment triangle of PQR, by the definition of midsegment: ST = _ 1 PR; SU = _ 1 QR; TU = _ 1 QP Therefore, STU PQR by SSS similarity. - 3 S 19 Q + 7 T b. Find PQ. P U R QR is twice SU, and T is the midpoint of QR, so QT = SU. + 7 = 19 = 6 Since S is the midpoint of PQ, PQ = PS. PQ = ( - 3) = [(6) - 3] = The length of PQ is units. Lesson

29 ample 5 pplication: Maps student determined that Toledo Street is the midsegment of the triangle formed by olumbus venue, Park venue, and William Street. The distance along Park venue between olumbus venue and William Street is 160 meters, and the distance along Toledo Street in the same span is 80 meters. William Street is 0 meters long. Find the distance from the corner of olumbus and William to the corner of William and Toledo ( in the diagram) to the nearest meter. olumbus venue Toledo Street Park venue 160 m 80 m 0 m William Street Since Toledo Street is the midsegment of the triangle, it creates two similar triangles. Use the lengths of Toledo Street and Park venue to find the similarity ratio of 160:80. Name the shorter segment and write a proportion. _ = _ = (80)(0) = 10 m Lesson Practice ( 1) a. TU is a midsegment of QRS. Find the values of and y. y T 8 R 1 U Q S Hint This proof is similar to the proof of Theorem 55-1, given in ample. Start by showing that the two triangles in the diagram are similar. ( ) b. Prove Theorem 55-. Given: and is the midpoint of. Prove: is the midpoint of. 36 Saon Geometry

30 ( 3) ( ) c. Triangle FGH has vertices at F(-, ), G(6, ), and H(,-1). is a midsegment of FGH. Find the coordinates of and. d. Find the perimeter of the midsegment triangle, XYZ. 5 1 X Z F(-, ) O y G(6, ) 6 H(, -1) + Y 3 + ( 5) e. In the diagram, th Street is a midsegment of the triangle formed by aker, Lowry, and 5th Streets. Jeremiah leaves his house at the corner of 5th and aker and walks down 5th Street. He then turns left and walks up Lowry Street until he reaches the corner at Lowery and th Street. How far has Jeremiah walked? aker Street th Street 11 m 5th Street 10 m Lowery Street Practice istributed and Integrated * 1. raw a triangular prism in one-point perspective so that the vanishing point (5) is below the prism.. Multiple hoice Which of the following statements is not true of a rhombus? ll sides are congruent. The diagonals are perpendicular. The diagonals are congruent. The diagonals bisect the angles. (5) 3. Model Trains Gary is building a track for his model trains. He wants to ensure that the two sides of the tracks run parallel to each other, so he places crossbeams at regular intervals along them. What could Gary check to ensure the tracks are parallel? (Inv 1). rror nalysis fter reading the Triangle Inequality Theorem, which states that the sum of the lengths of any two sides of a triangle is greater than the length of the third side, Ken reasons that the theorem would mean the same if it were written, The sum of the lengths of any two sides of a triangle cannot be less than the length of the third side. Is Ken correct? plain. (39) * 5. Trace the figure shown on your paper. Then draw the vanishing points and the (5) horizon line of the figure. 6. nalyze In which regular polygon is each eterior angle equal to each interior angle? (Inv 3) Lesson

31 7. How many edges does a figure with 8 vertices and 6 faces have? (9) 8. viation pilot determines that after flying 00 kilometers on one leg of a trip and 5 kilometers on a second leg of a trip, that she has enough fuel to fly another 715 kilometers. oes she have enough fuel to get back to her starting point? plain. (39)? 00 km 5 km * 9. nalyze Give a paragraph proof showing that if a triangle is equiangular, then it is (51) equilateral. 10. Golf In his first shot of a golf tournament, illustrated here, Mitch has hit the ball (53) too far to the left from where it should be. How far does he need to hit the ball to get it straight to the green from where it is now? Give your answer to the nearest tenth of a yard. still to go 1st shot green 135 yard 5 tee *11. raw a cube in two-point perspective. (5) *1. Segment is a midsegment of. (55) Refer to the diagram to determine the coordinates of and. 13. In QRS, m Q = 55, and m R = 86. (6) In TUV, m T = 55, and m V = 39. Is QRS TUV? plain. y (3, ) (-, 3) (0, -) - 1. The ratio of the angle measures in a quadrilateral is 1::5:6. Find the measure (1) of each angle. *15. Segment UT is a midsegment of XYZ. Find the values of and y. X (55) y 16. Multi-Step Find the orthocenter of GHI with vertices G(-8, -9), H(-, -1), (3) and I(-, -9). T U Find the geometric mean of 1 and 5. (50) 5-1 y 18. lgebra Solve the equation ( + 3) =. Provide a justification for 3 () 366 each step. Saon Geometry Z 30 Y

32 19. nalyze triangle has vertices L(0, 0), M(8, 0), and N(, y). What value of (5) y makes LMN equilateral? * 0. Write plain why the median and the altitude from the verte angle of an (51) isosceles triangle are identical. Refer to any theorems you need to justify your eplanation. * 1. elow is the beginning of a paragraph proof of the Triangle Inequality (31) Theorem. Write the rest of the proof. Hint: Use the Isosceles Triangle Theorem. Given: Prove: + >, + >, + > One side of is as long or longer than each of the other sides. Let this side be. Then + > and + >. Therefore what remains to prove is + >. Locate on such that = If a chord is bisected inches from the center of a circle with a diameter of (3) 6 inches, what is the length of half of the chord to the nearest tenth of an inch? y 3. lgebra Find the measure of ST in the circle at right. y (7) *. The midpoints of the sides of are as follows: midpoint of (55) : (, 1); midpoint of : (1, 3); and midpoint of : F(1, 0). raw the midsegment triangle. Find the coordinates of,, and, and then draw. S (7 - ) V U T (5 + 0) 5. Travel Marco travels from Yuma to lamo and then from lamo to (53) Gadsden. ach unit on the triangle represents 30 miles. How far does he need to travel to get from Gadsden to Yuma, if he were to travel a straight path between them, rounded to the nearest mile? lamo y 5 units 5 Yuma 6. Landscaping square field is to be hydro-seeded. The field has a (53) diagonal length of 5 yards. How many square feet need to be hydro-seeded? Gadsden 7. etermine if these two triangles are similar. If so, state the similarity (6) and the reason. 8. Find the geometric mean of 11 and 1.5. (50) 9. Write Sketch this situation or eplain why it is impossible. Two parallel lines are intersected by a transversal so that the same-side interior angles are complementary. (Inv 1) J M 1 N L 8 K 16 y 30. lgebra Points Q, R, and S are midpoints of FGH. If FH = + 1 (55) and QR = - 3, what is the length of QR? G R Q F S H Lesson

33 56 LSSON Right Triangles Warm Up 1. Vocabulary (n) triangle has three sides that are congruent.. If a right triangle has a hypotenuse of 13 centimeters and a base of 5 centimeters, what is its height? 3. If an isosceles triangle has a verte angle of 0, what is the measure of a base angle? (51) (9) (51) New oncepts The triangle is another special triangle. Like the triangle, properties of the triangle can be used to find missing measures of a triangle if the length of one side is known. Math Reasoning onnect triangle can be used to prove attributes in a square. What quadrilaterals can be formed using triangles? In the diagram, two triangles are shown net to each other, with the shorter legs aligned Placing the two triangles together so that they share a common leg makes an equilateral triangle. Since all the equilateral triangle s sides are congruent, this shows that the hypotenuse of the triangle is twice the length of the shortest leg. Properties of Triangles In a triangle, the length of the hypotenuse is twice the length of the short leg, and the length of the longer leg is the length of the shorter leg times lgebraically, these relationships can be written as follows. PR = a PQ = a QR = a 3 Q 30 Online onnection ample 1 Finding Side Lengths in a a a Triangle 60 P Find the values of and y. Give your a R answer in simplified radical form. y The shortest leg must be opposite the smallest angle, so the leg with a measure of is the short leg. The hypotenuse is twice the short leg, so y =. The long leg is 3 times the short leg, so = Saon Geometry

34 ample Finding the Perimeter of a Triangle with Unknown Measures Find the perimeter of the triangle. Give your answer in simplified radical form. 30 y 10 cm 60 aution s in Lesson 53, be sure to rationalize any fraction with a square root in the denominator by multiplying both the numerator and denominator by that root. First, find the length of and y. The short leg is. Since the length of the short leg times the square root of 3 equals the long leg, an equation can be written to solve for. 3 = 10 = _ 10 3 _ = Since the length of the short leg is now known, the length of the hypotenuse can be found by multiplying the short leg by. y = y = (_ ) y = _ Now that the lengths of all the sides are known, calculate the perimeter. P = s 1 + s + s 3 Formula for perimeter P = 10 + _ _ 0 3 Substitute. 3 3 P = Simplify. Instead of memorizing the algebraic epressions for each side of a triangle, it may be helpful to just remember the triangle in the diagram, with side lengths 1, 3, and Lesson

35 Math Reasoning nalyze If the side length of each tile were to double, what would happen to the area? ample 3 pplying the Pythagorean Theorem with Right Triangles ach tile in a pattern is an equilateral triangle. Find the area of the tile. Use the Pythagorean Theorem and 30 give your answer in simplified radical form. 5 in. h a + b = c 60 Pythagorean Theorem + ( 3 ) = 5 Substitute. = 5 Simplify. _ = _ 5 ivide both sides by. = _ 5 Simplify. = _ 5 Simplify. Since h is the longer leg of the right triangle, its length is equal to the length of the shorter leg times 3. So, h = _ 5 3, or _ 5 3. Find the area of each tile. = _ 1 bh Triangle rea Formula = ( _ 1 _ 3 ) Substitute. = _ ) ( 5 ) ( 5 _ Simplify. ouble the answer because only half the area of the tile has been found. T ( = _ ) T = _ 5 3 in Notice that the sides match the ratios. ample pplication: ngineering museum ehibit contains a model of a pyramid. It has equilateral triangles for faces, and each side of a face is 3 feet long. For a restoration project, the ehibit designers need to know the area of one face of the pyramid. Find this area. 3 ft y 370 Saon Geometry

36 Math Reasoning Model This gives the area for one face of the pyramid. How can the area of all the visible faces of the pyramid be found? First, find the dimensions of the triangle. Set up an equation to solve for. = 3 = 3 _ Hypotenuse of a is twice the shorter leg Simplify. Use the value for to find y, the longer leg of the triangle. y = 3 Longer leg of a is 3 times the shorter leg y = _ 3 3 Substitute. Net, find the area of the triangle. = _ 1 bh Triangle rea Formula = _ 1 _ 3 ) Substitute. _ ( 3 ) ( 3 _ = 9 3 Simplify. 8 T = (_ ) Multiply by to find the area of one face. _ T = 9 3 ft Lesson Practice ( 1) ( ) a. Find the length of each side of the triangle. b. Find the perimeter of the triangle in simplified radical form. y 7 y ( 3) ( ) c. school s banner is an equilateral triangle shown here. Use the Pythagorean Theorem to find the area of the equilateral triangle. d. Find the area of one triangular face of a pyramid. The faces of the pyramid are equilateral triangles with sides that are 1 centimeter each. 1 in. Practice istributed and Integrated y (7) y 1. lgebra Find m F in the figure at right.. Write plain why the following statement is true. (5) If a quadrilateral is a square then it is a rhombus. I H (5) (8) (10) G F (13) Lesson

37 * 3. Find the hypotenuse of a triangle if the shorter leg is (56) centimeters long. *. Trace the figure at right on your paper. Then locate and (5) draw the vanishing points and the horizon line. 5. Multiple hoice What is the area of a net for a cube with edges that are 3 centimeters long? 7 cm 5 cm 36 cm 7 cm (Inv 5) 6. Find the length of if = 9, = 6, and = 1. (38) * 7. The midpoints of the sides of PQR are as follows: midpoint of (55) PQ: S(3, 1); midpoint of QR: T(1, -1); and midpoint of RP: U(-1, 1). raw the midsegment triangle. Find the coordinates of P, Q, and R, then draw PQR. y 8. lgebra Find the measure of in the diagram. (7) * 9. Multiple hoice Which set of sides does not make a (56) triangle?, 8, 3 3, 3, 3 3, 6, 3 3 3, 3, 3 ( + 16) ( + 30) ( - 18) ( - 3) 10. What is the sum of the interior angles of a conve dodecagon? (Inv 3) 11. Justify plain how you know the two triangles shown are similar, and then (6) write the similarity statement. G H 3 J 1. Find the geometric mean of 1.55 and 5.. (50) Find the eact value of the length of the side of a (53) right triangle with a hypotenuse of 15 miles. 1. In F, F. (51) a. Write a congruence statement involving the sides of F. b. The perimeter of F is 35 millimeters, and F = 1 millimeters. etermine. 9 L K 15. rror nalysis Triangle PQR has verte P at the origin. Vertices Q and R are (5) equidistant from P, and R has coordinates (, -6). Nasim says that Q must have coordinates (6, ). Is Nasim correct? plain. y 17. lgebra ach base angle of an isosceles triangle measures (67-3y). (51) 37 a. lassify the base angles. b. Write and solve an inequality for y. Saon Geometry eisting roads coast line 1.8 miles 5 coast line 16. Survey Science The diagram shows a new bridge that is being built (53) across a section of coastline. Given the surveyors measurements of the eisting road and the bridge span, by how much distance will the bridge reduce the trip, to the nearest tenth of a mile?

38 * 18. raw a triangular prism in one-point perspective so that the vanishing point is (5) above the prism. * 19. Segment VW is a midsegment of XYZ. Find the coordinates of (55) V and W. * 0. Playgrounds slide forms the hypotenuse of a triangle (56) with the ground. If the slide is 15 feet long, how long are the other two sides of the triangle? 1. Justify Write formulas for finding arc length and area of a sector of given (35) m central angle m. plain why the coefficient is *. Multi-Step triangle has coordinates of (1, 1), (, 1), and (3, ). etermine whether (56) or not this is a triangle nalyze If the angle bisector of one angle of a triangle is also the perpendicular (38) bisector of the opposite side, what can you conclude about the triangle?. Plant Growth scientist conducted an ay (7) eperiment to see which of two plants grew Plant faster. She recorded her results as shown. 1 cm cm cm 6 cm 7 cm 8 cm Height a. What conjecture could be reasonably Plant drawn from the data? 1 cm cm 3 cm cm 5 cm 6 cm Height b. What alternate conjecture could you draw that is consistent with the data but incompatible with the first conjecture? -8 Z(-1, 1) y 8 - W - -8 V Y(8, 6) 8 X(5, -) * 5. Segment is a midsegment of. Find the values of and the lengths (55) of and. 6. Generalize The general form of a nonvertical line in slope-intercept form is (37) y = m + b. What is the general form of a line perpendicular to y = m + b, in slope-intercept form? etermine whether the set of measures (1, 15, 16) can be the side lengths of a triangle. If these measures could be a triangle, determine whether it is an acute, obtuse, or a right triangle. (33, 39) 8. Photography photographer is developing a picture of a building which is () 108 feet tall. a. What is the relationship between the building and the image of the building in the photograph? b. If the image of the building in the photograph is 1 inches tall, what is the similarity ratio between the building and its image? y * 9. lgebra The hypotenuse of a triangle has a length of r. What are the (56) lengths of the other two legs? 30. esign The math faculty of Pythagoras ollege uses this square (18) logo. One acute angle measure in each right triangle is 37. a. etermine the measure of 1. b. etermine the measure of Lesson

39 57 LSSON Finding Perimeter and rea with oordinates Warm Up 1. Vocabulary The is the distance a number is from zero. (). Find the distance between points and () on the number line Find the distance between the points (-, 5) and (, 8) to the nearest (9) hundredth. New oncepts When a figure is on a coordinate plane and no measurements are given, the distance formula can be used to determine the measurements necessary to find the area or perimeter of the figure. Hint The distance formula for finding the distance between points ( 1, y 1 ) and (, y ) is: d = ( - 1 ) + ( y - y 1 ) ample 1 Finding Perimeter with oordinates Find the perimeter of the rectangle with coordinates (, ), (, -), (3, -) and (3, ). y O - - Plot the given points on a coordinate plane - and draw the rectangle. To find the perimeter, find the length of each side. The distance formula can be used, but since all the segments that compose the rectangle are vertical or horizontal, the length of each segment can be calculated as if it were on a 1-dimensional number line. = y 1 - y = - (-) = 6 Since the figure is a rectangle, also has a length of 6. The shorter sides, and, have lengths of 1. P = P = 1 Online onnection ample Finding Perimeter with the istance Formula Find the perimeter of rectangle FGH with coordinates (1, 3), F(, 0), G(-, -), and H(-5, 1). Give your answer in simplified radical form. H G - y O - - F 37 Saon Geometry

40 Plot the points on a coordinate plane. Then use the distance formula to calculate the length of each side. d = ( - 1 ) + ( y - y 1 ) d F = ( - 1) + (0-3) d F = 10 gain, because the figure is a rectangle, F and HG are congruent. Net, use points F and G to find the length of the rectangle s longer side. d FG = ( - - ) + (- - 0) d FG = 10 Finally, find the perimeter by summing the four sides. P = P = 6 10 rea can be found on a coordinate plane in the same way. It is important to know what kind of polygon a figure is before attempting to find its area. Though a figure may look like a rectangle, you cannot assume it is unless you are given that information in the problem or you can prove that the adjacent sides of the figure are perpendicular to each other. Math Reasoning Formulate How can you verify that is a right angle? ample 3 alculating rea with oordinates Find the area of right triangle with right angle. Since we know the triangle is a right triangle, finding the length of the two legs is sufficient to find the area. Since is the right angle, the legs are and. Use the distance formula to find the length of each segment. y d = ( - 1 ) + ( y - y 1 ) d = (3-1) + (-1-3) d = ( -1-1) + ( - 3) d = 5 d = 5 Now the formula for area of a triangle can be applied using and. = _ 1 bh = _ 1 ( 5 )( 5 ) = O - - Lesson

41 Math Reasoning stimate circle has a radius of units. Using the coordinate grid, estimate the area of the circle and then calculate the actual area using = π r. How close was your estimate? Sometimes it may be necessary to find the area of an irregular polygon. coordinate plane makes this possible, because each square on the grid can be counted and added together to find the area of a figure. When a square is not entirely inside a polygon, it may be necessary to estimate and obtain an approimate area. ample stimating rea with oordinates a. stimate the area of the polygon. First, count all the squares that lie completely inside the polygon. There are 10 squares that are completely covered, as shown in the diagram Net, estimate the area of the remaining space. One way to do this is to look for triangles, like the right angle shown in the diagram. The triangle s legs measure 1 and, so the area of this triangle is 1 square unit. 1 Two identical right triangles together make a rectangle. ach of these right triangles has one leg that is three squares long and one leg that is one square high. Together, they make a rectangle with an area of 3 square units stimate the remaining area. y looking at the remaining rectangle, which appears to have a height of approimately 0.5 and length of 3, plus the two remaining triangles, it appears that the remaining area is about 3 square units. dd all these items together. The total area of the polygon is approimately 17 square units Saon Geometry

42 b. stimate the area of the figure. First, count complete square units. There are 1. Then, estimate the area of the remaining area. The curved area covers around one square unit on either side. Therefore, the total area is approimately 16 square units. aution cres measure area, not length. Therefore, there is no such thing as a square acre. ample 5 pplication: Farming farmer wants to estimate how much seed she needs to buy for her land. She cannot farm in the river or on the riverbank, which is shaded in the diagram. For every acre, she needs bags of seed. stimate how many bags of seed she will need. ach square unit on the grid represents one fourth of an acre. The entire plot of land is 9 by 13, or 117 units. very four units equals one acre. Including the river, the farmer has 117 = 9.5 acres. There are 9 full units that are unusable because of the river and riverbank, as shown in the diagram. Net, identify triangles and their approimate measurements. The remaining parts of the river and riverbank add to approimately 1 square units. Your answers may vary, but anything between 13 and 15 units is a reasonable estimation. = 1 acre = 1 acre Therefore, the total amount of land that is not available for farming is approimately 63 square units. very four units equals one acre, so there are 63 = acres that are unusable. In total, she can use = 13.5 acres. The farmer will need 13.5() = 7 bags of seed. Lesson

43 Lesson Practice a. Find the perimeter of rectangle LMNO with coordinates L(-5, 3), M(-5, -1), N(, -1), and O(, 3). ( 1) b. Find the perimeter of triangle PQR with coordinates P(, -1), Q(9, 3), and R(6, -). Round your answer to the nearest hundredth. ( ) c. alculate the area of XYZ. ( 3) y Y X O Z d. stimate the area of the figure. ( ) e. The school committee wants to put gravel on its new running path. stimate the amount of gravel they must buy if every square meter of path requires 0 kilograms of gravel. ( 5) Practice istributed and Integrated 1. Generalize In a right triangle, what is the ratio of the length of the leg opposite the 30 angle to the length of the hypotenuse? What is the ratio of the length of the leg opposite the 60 angle to the length of the hypotenuse? press your answers both eactly and to the nearest thousandth. (56). What would be necessary information to add to the Side-Side-Side Similarity Theorem to transform it into the Side-Side-Side ongruence Theorem? (6) 3. lueprints n architect is drawing up plans for a house. The house should have a storage closet with a triangular floor area. If the actual closet s area is to have dimensions of 10 feet, 6 feet, and 8 feet, and the architect s drawing has a longest side of 6 3 inches, what are the side lengths of the other two sides of his drawing? () 378 Saon Geometry = 1 m

44 y. raw a cube in one-point perspective with a vanishing point below the cube. (5) * 5. Find the area of with vertices (, ), (, 5) and (-5, 1). (57) y (3) 6. lgebra Find the distance from the center of a circle with a 10-centimeter radius to a chord that is 13 centimeters long to the nearest tenth. 7. Show that lines m and n in this figure are parallel. (1) * 8. Find the perimeter of quadrilateral WXYZ if (57) W (, ), X(-, 3), Y(-1, 7), and Z(, 9). Give your answer in simplified radical form. 9. Multiple hoice What is the approimate area of a sector of a circle with a radius of 6 units and an arc measure of 60? (35) 10. Justify Find in the parallelogram at right, and justify each step. (3) 11. Framing photographer is building a frame for a square picture. (53) In order to have the picture frame stand upright, a collapsible stand must be attached to the back that folds eactly across the diagonal of the back. If the frame is 8 inches on a side, how long must the stand be? Give your answer in simplified radical form and rounded to the nearest tenth. l m n y (7) y 1. lgebra Find the measure of G in the circle at right. 13. nalyze Prove the onverse of the Hypotenuse-ngle (36) ongruence Theorem. 5m H 1. Find the distance from (-1, 1) to the line y = 5. () I 8m 10m G F 15. Verify Segment JK is a midsegment of FGH. Find the coordinates of (55) J and K. Use the distance formula to verify that JK is half the length of GH. 16. utomotive ngineering n engineer needs to make a model of () a car s triangular window that has side lengths of, 1, and 18 inches long, respectively. If the designer s model has the shortest corresponding side of the window measuring inches, what are the lengths of the other two sides of the window? *17. What is the perimeter of a triangle with a shortest side (56) length of 3. inches? 18. What is the negation of, If q, then p? (17) 19. Verify In, show that if and are the midpoints of (55) their respective sides by finding the slopes of the segments. F(-3, 5) y J K G(3, 1) O - - H(-1, -1) - - (1, 5) y - - (-1, -1) - - (3, -3) Lesson

45 * 0. Multi-Step Find the area of a polygon with vertices J(, ), K(-3, ), L(0, -) (57) and M(, 1). 1. etermine the value of in the circle at right. (3). Multiple hoice Which statement contradicts the fact that (8) HIJ F? HI = r for some factor r H = H F None of the angles in HIJ have the same measure as any of the angles in F. 15 O 9 3. rror nalysis arina marked the triangle at right in order to find the centroid. (3) plain the error she made. *. Industrial Painting painter needs to paint a triangular ramp. (56) The ramp is inclined at 30 to the ground and is 30 feet high. If it takes the painter 1 minute to paint square feet on average, how long will it take him to paint the side of the ramp, to the nearest minute? ft * 5. Justify Which is the larger angle in the figure shown, or? (Inv ) plain your answer. * 6. Urban Planning city block is on a grid. If the corner of a rectangular (57) building is at (9, 0) and another corner is 7 units to the left and 6 units up from that corner, what are the other coordinates of the building and what is its perimeter? 7. nalyze What is the fewest number of regular triangular tiles necessary to form (9) a polyhedron, and what is the name of the polyhedron formed? 3 8 * 8. Write a paragraph proof showing that in a circle or congruent circles, chords (31) equidistant from the center are congruent. Given: and are equidistant from P. (i.e. PX = PY ). Prove: 9. Prove that lines d and e in this figure are parallel if m 1 = 63 and (1) m = 117. d e P y c 1 * 30. Write The hypotenuse of a right triangle is 3 meters and one leg is 16 meters. (56) second right triangle has a 60 angle. How can you use this information to find whether these triangles are similar? an it be determined whether these triangles are congruent? 380 Saon Geometry

46 58 LSSON Tangents and ircles, Part 1 Warm Up 1. Vocabulary segment whose endpoints lie on a circle is a of the circle.. and are radii of. lassify by its sides. (3) (13) 3. Which line is a tangent to? Which line is a secant to? (3) m p n New oncepts tangent line lies in the same plane as a circle and intersects the circle at eactly one point. radius of a circle drawn to a point of tangency meets the tangent line at a fied angle. Math Language Theorem 58-1 point of tangency is a point where a tangent line intersects a circle. If a line is tangent to a circle, then the line is perpendicular to a radius drawn to the point of tangency. F G radius G F tangent ample 1 Tangent Lines and ngle Measures Line n is tangent to at point P, and line m passes through. Lines n and m intersect at point Q. a. Sketch and lines n and m. Mark, P, and Q on your sketch. Q P n m b. If m QP = 36, determine m PQ. Online onnection y Theorem 58-1, P is perpendicular to n, so PQ is a right triangle. Therefore, QP and PQ are complementary. m QP + m PQ = m PQ = 90 m PQ = 5 Lesson

47 Theorem 58- If a line in the plane of a circle is perpendicular to a radius at its endpoint on the circle, then the line is tangent to the circle. ST is tangent to V. S radius V U T Math Reasoning Theorem 58- is the converse of Theorem Together, they can be used to show that this biconditional statement is true: line in the plane of a circle is tangent to the circle if and only if it is perpendicular to a radius drawn to the point of tangency. Write State the inverse of Theorem Is it true or false? ample Identifying Tangent Lines If m = 5, show that is tangent to. To show that is tangent to, it has to be shown that is a right angle. From the diagram, is an isosceles right triangle, so. The acute angles of a right triangle are complimentary, so both and are 5 angles. y the ngle ddition Postulate, + =. Substituting shows that = 5 + 5, so is a right angle. Therefore, by Theorem 58-, is tangent to. ample 3 Proving Theorem 58- Prove Theorem 58-. Given: F and is on. Prove: is tangent to. F We will write an indirect proof. ssume that is not tangent F. Then intersects F at two points, and point P. Then F = FP. ut if FP is isosceles, and the base angles of an isosceles triangle are congruent, then PF is a right angle. That means there are two right angles from F to, which is a contradiction of the theorem which states that through a line and a point not on a line, there is only one perpendicular line, so the assumption was incorrect and is tangent to F 38 Saon Geometry

48 Math Reasoning Model If tangent lines are drawn to the endpoints of a diameter of a circle, where will they intersect? If two tangents to the same circle intersect, the tangent segments ehibit a special property, stated in Theorem Theorem 58-3 If two tangent segments are drawn to a circle from the same eterior point, then they are congruent. MQ NQ Q M N P ample pplying Relationships of Tangents from an terior Point In this figure, JK and JM are tangent to L. K 17 in. L 8 in. J M etermine the perimeter of quadrilateral JKLM. What type of quadrilateral is JKLM? Since ML and LK are radii of the same circle, KL = 8 in. y Theorem 58-3, tangents to the same circle are congruent, so JM = 17 in. To get the perimeter, add the lengths of the four sides. P = JK + KL + LM + JM P = = 50 in. Since JKLM has eactly two pairs of congruent consecutive sides, it is a kite. ample 5 pplication: Glass utting n ornamental window has several glass panes oriented to look like an eye. The radius of the eye s iris is 3 feet, and is 5 feet. What are I and H? 5 H I 3 F The right angles on the diagram indicate that the four segments that form the corners of the eye are tangent to the circle. raw in the segment F. This forms right triangles, FI and FH. The hypotenuse of the triangles are 5 feet long, and their shorter legs are each 3 feet long. y using the Pythagorean Theorem, I and H are each feet long. 5 H I 3 F Lesson

49 Lesson Practice ( 1) ( ) ( ) ( ) ( 5) a. Line a is tangent to R at, and line b passes through R. Lines a and b intersect at. If m R =, determine m R. b. Let be a radius of. Let line m be tangent to at. Let be an eterior point of, with m < 90. Is a tangent to? Why or why not? c. Give a paragraph proof of Theorem Hint: raw P, P and P. Given: and P are tangent to P Prove: d. ircle has a 5-inch radius. XZ and YZ are tangents to and Z is eterior to. If XY is a right angle, what is the area of quadrilateral XZY? e. decorative window is shaped like a triangle P with an inscribed circle. If the triangle is an equilateral triangle, the circle has a radius of 3 feet, and Q is 6 feet, what is the perimeter of the triangle in simplified 3 6 radical form? R Q Practice istributed and Integrated * 1. In this figure, and Z are the centers of the circles. P is parallel to ZQ and (58) perpendicular to PQ. Is PQ tangent to and/or Z? plain. *. Find R if FG = 36. (58) R P Q Z F 60 * 3. stimate stimate the area under the curve y = for 0 6. (57) G 6 y *. Multi-Step Find the perimeter of a triangle in which the shorter (56) leg is 7 feet. Give your answer in simplified radical form. 5. Three fire stations are located at the vertices of a triangle as shown. Which two stations are located farthest apart? (39) O 6 1 ( + 0) ( - 5) 3 38 Saon Geometry

50 6. Write In UVW, UW = 3.5 inches and V is a right angle. In XYZ, m Z = 90, m X = 33 and m Y = 57. The Hypotenuse-ngle ongruence Theorem can be applied if two additional measures are known. What could they be? plain. (36) 7. ividing ost Hubert and three friends bought a rectangular pizza that cost $10 for each of them to share, but the slices were not cut evenly. If the shaded region of this figure represents the portion of the pizza Hubert ate, what amount of money should he pay for his portion of the pizza? (0) 8 in. in. in. 8 in. 10 in. 8. Generalize Two segments of different lengths are attached perpendicularly at the midpoint of each segment. If you draw in the segments that connect all of the endpoints of the segments, what kind of a quadrilateral appears? How would the shape differ if both segments were of the same length? (5) 9. Indirect Measure ngelique wants to measure the diameter of a large circular pool, but she cannot reach the center. ngelique has two large pieces of rope. plain how she can use her knowledge of chords to find the diameter. (3) y 10. lgebra The lengths of three line segments are given by the epressions 3 +, (39) and. an these segments be used to create a triangle if =? if = 6? y 11. lgebra Points J, K, and L are midpoints of FGH as shown. If GH = 5 + (55 and KL = 3 -, what is the length of GH? G 1. Framing erek made a frame for a picture that is 15 inches long and (9) 8 inches wide. He wanted the frame to be a square, but now he thinks his earlier measurements were wrong. In order to determine if the frame he made is a square, erek measured the diagonals to be 17.6 and inches each. With these dimensions, is the frame a square? If not, by how many inches are erek s measurements off? F K L J H *13. Line p is tangent to N at X, and line q passes the center of N. (58) Lines p and q intersect at Y. a. Sketch N, lines p and q, and points X and Y. b. If m XNY = 13, determine m NYX. *1. XYZ has vertices Y(-5, ) and Z(0, ). ZYX is a right angle, and (56) m YZX is 60. Find the coordinates of X if X is in Quadrant II. 15. Multi-Step In equiangular LMN, LN = 17 inches. etermine the perimeter (51) of LMN. Give your answer in feet and inches. 16. raw a cube in two-point perspective so that the horizon line and vanishing (5) points are below the vertical line. 17. Multiple hoice Which of the following is perpendicular to + y = 6? (37) + y + 7 = 0 7 = 15y + 6 ( + 6) - 8y = 0 - y = Lesson

51 *18. etermine the perimeter of this quadrilateral if U is the center of (58) the circle. 19. Jose started at his home, H(0, 0) and walked to a park located at (57) P(, ). He then went to Jacintha s house located at F(8, 0). Later, he walked straight home. If each unit on the coordinate plane represents 50 feet, what is the distance that Jose walked, to the nearest foot? U 73 mm mm 0. rror nalysis Noyemi said the following statement is sometimes true. (5) Is she correct? plain. If a quadrilateral is both a rectangle and a rhombus, then it is a square. 1. Find the measure of in M given that m M = 7. (7). Multiple hoice n isosceles triangle has a base and height that are (51) centimeters each. The length of each leg is: centimeters 3 centimeters 5 centimeters 3 centimeters M 3. Floor Plans floor plan for a square shed was left unfinished. (53) However, Lisa can see that the diagonal of the shed is 7 feet. How many 6-foot long pieces of lumber does she need to form the perimeter of the shed?. quadrilateral inscribed in a circle has interior angles of 55, 90, 5, and 18, (7) in clockwise order. Find. * 5. Traffic Signs n equilateral yield sign has a height of 1 foot. What is the area (56) of the sign in simplified radical form? 6. What is the included angle of sides XY and ZX in a triangle? (RN) * 7. stimate the area of the irregular shape in the diagram. (57) 8. Write In parallelogram, is drawn to create (5) and. re these triangles congruent? plain. 1 ft 9. Predict If two congruent septagonal prisms are joined together at their (9) bases, with their bases aligned, what is the resulting shape? 30. Justify Given the information in this diagram, could RT be greater than TS? If so, find the range of values when this is true. If not, eplain your answer. (Inv ) (5-8) Q ( - ) R T S 386 Saon Geometry

52 8L Tangents to a ircle onstruction Lab 8 (Use with Lesson 58) Lesson 58 shows you how to identify lines tangent to a circle. This lab demonstrates how to construct lines tangent to a circle through a point on the circle. 1. To construct a tangent line through a given point on the circle, begin with and a point on the circle,. 1. raw. 3. Using the method from onstruction Lab, construct the line perpendicular to through. 3 The perpendicular line is tangent to at. This lab demonstrates how to construct lines tangent to a circle through a point not on the circle. 1. To construct two tangent lines through a point eternal to a circle, draw a circle and label the center. hoose a point eterior to the circle, and label it P. raw P. 1 P Lab 8 387

53 Hint To construct the midpoint, use the method you learned in onstruction Lab 3.. onstruct the midpoint of P. Label the midpoint M. M P 3. raw a circle with a radius, M centered on M. Notice that P is also on this circle. 3 &. Label the points of intersection of and M as points X and Y. X M P Y 5. raw XP. This line is tangent to at point X. raw YP. Notice that YP is tangent to at point Y. 5 X M P Y Lab Practice Use a compass to draw and. raw point on. raw points F and G outside, but near to, and. Perform each construction indicated below. a. a line tangent to at point b. a line tangent to from point F c. a line tangent to from point F d. a line tangent to from point G 388 Saon Geometry

54 59 LSSON Finding Surface reas and Volumes of Prisms Warm Up 1. Vocabulary polyhedron formed by two parallel congruent polygonal bases connected by lateral faces that are parallelograms is called a. (9). Find the area of the triangle. (13) 10 in. 11 in. 3. Find the area of a 1-by-7-foot rectangle. () 8 in. New oncepts The surface area of a solid is the total area of all its faces and curved surfaces. The surface area of the pentagonal prism shown in the diagram, for eample, is the sum of the area of the two pentagons and the five rectangles that compose the prism. Math Reasoning Formulate The bases of a cylinder are circles. What would the formula be to find the lateral area of a cylinder? Lateral area is the sum of the areas of the lateral faces of a prism or pyramid, or the surface area, ecluding the base(s), of the lateral surface of a cylinder or cone. In the diagram, the lateral area of the pentagonal prism is the sum of the area of all the rectangular faces. Lateral rea of a Prism base base The lateral area L of a prism can be found using the following formula, where p is the perimeter of the base and h is the prism s height. L = Ph lateral faces lateral edges ample 1 Finding Lateral rea of a Prism Find the lateral area of the regular heagonal prism. Online onnection First find the perimeter of the base, then multiply it by the height. The base is a regular heagon with 6 side lengths of 1 feet each, so the perimeter is 7 feet. Net, multiply the perimeter by the height, or The lateral area of the prism is 196 square feet. 1 ft 18 ft Lesson

55 Hint Surface area of a prism can be calculated by finding the sum of the areas of each face. Sometimes it is easiest to first determine the lateral surface area and then add the area of the two bases to the lateral surface area. If the formula for lateral area or total surface area cannot be recalled, find the area of each face of a solid separately and then add them together. Surface rea of a Prism The surface area of a prism is the sum of the lateral area and the area of the two bases, where is the area of a base. S = L + ample Finding Surface rea of a Prism Find the surface area of the regular pentagonal prism. The base is a regular pentagon, so its perimeter is given by multiplying the length of each side by the number of sides. Therefore, the perimeter is 5 5 = 5 inches. Substitute the perimeter s value and the height 7 into the lateral area formula. L = ph L = (5)(7) L = 175 i n 5 in. 7 in. 3. in. Now find the area of the base, which is a pentagon. The pentagon can be divided into five congruent triangles as shown. For one triangle: = 1 _ bh = 1 _ (5)(3.) 8.6 i n So the area of the base is about (5)(8.6) = 3 square inches. To find the total surface area of the prism, use the formula for surface area. S = L + S = ()(3) = 61 i n So the surface area of the prism is 61 square inches. Surface area can be considered as the number of square units it takes to eactly cover the outside of a solid. Volume is the number of unit cubes of a given size that will eactly fill the interior of a solid. Volume of a Prism The volume of a prism can be found using the formula below, where is the area of the base and h is the height of the prism. V = h 390 Saon Geometry

56 right prism is a prism whose lateral faces are all rectangles and whose lateral edges are perpendicular to both bases. In a right prism the height is the length of one edge that separates the bases. ample 3 Finding the Volume of a Right Prism Find the volume of the right prism. 9 ft 8 ft 1 ft 5 ft aution When finding volume, an area measured in square units is multiplied by a length measured in units. The result is a volume, epressed in cubed units or, unit s 3. The base of a prism is a trapezoid, so calculate the area of the base first, then the volume of the prism: = _ 1 ( b 1 + b )h = _ 1 (8 + 1)5 = 50 f t V = h V = (50)(9) = 50 f t 3 The volume of the prism is 50 cubic feet. n oblique prism is a prism that has at least one nonrectangular face. n oblique prism is like a prism that has been tilted to one side. The surface area and the volume of an oblique prism are found using the same formulas that are used with a right prism. Instead of using the height of a lateral edge of the prism, an altitude of the prism must be used. n altitude of a prism is a segment that is perpendicular to, and has its endpoints on, the planes of the bases. height Oblique triangular prism ample Finding the Volume of an Oblique Prism Find the volume of the oblique prism shown. The volume of an oblique prism is the area of 8 in. the base times the height. o not use the slanted height of the lateral face. Instead, use the altitude, which is 8 inches. V = h V = _ 1 (6)() 8 V = 8 i n 3 The volume of the oblique triangular prism is 8 cubic inches. 11 in. in. 6 in. Lesson

57 ample 5 pplication: Packaging Rick has a gift that he needs to wrap. He has 15 square feet of wrapping paper. oes Rick have enough wrapping paper to cover the gift shown in the diagram? First find the lateral surface area by multiplying the perimeter of the -by-3-foot base by the height. L = ph L = ( ) (1) L = 10 f t Now add the area of the two bases. S = L + S = (10) + ()(3) S = f t Since the surface area of the gift is square feet, Rick will need to buy more wrapping paper to wrap the entire gift. Lesson Practice Use the figure at right to answer problems a and b. a. Find the lateral area of the prism. ( 1) ft 3 ft 1 ft ( ) b. Find the surface area of the prism. 15 yd 7 yd 9 yd ( 3) c. Find the volume of the right prism. cm 1 cm 10 cm ( ) d. Find the volume of the oblique prism. 5 ft 3 ft 1 ft 39 Saon Geometry

58 ( 5) e. Jennifer is filling her swimming pool, shown in the diagram. How many cubic meters of water will it take to fill the pool? 8 m 15 m m Practice istributed and Integrated 1. stimate stimate the area under the curve of y = for Solve the proportion _ 9 p = _ 36 8 (57) (1) 3. Find the values of and y in the triangle shown to the nearest tenth. (50). raw a cube in two-point perspective so that the y (5) horizon line and vanishing points are above the vertical line. * 5. Write rmine needs to find the area of a square but does not have the (53) measurements of its sides; however, he does know the diagonal length of the square. plain how rmine can use this to find the area of the square. 6. esign t-shirt designer is painting this pattern on a shirt. If each square on the grid represents 1 inch on the shirt, approimately what is the area he must cover with paint? (57) 7 y 8 6 O y 6 8 * 7. omplete this indirect proof showing that G (8) q if a line is tangent to a circle, then the line is perpendicular to a radius drawn to the point of tangency. F Given: Line q is tangent to F at point G. Prove: q FG ssume that q is not perpendicular to FG. Then it is possible to draw F such that F q. If this is true, then FG is a right triangle. F < FG because. Since q is a tangent line, it can only intersect F at, and must be in the eterior of F, so F > FG. Thus the assumption is false, and. 8. rror nalysis To find the orthocenter of a triangle, Marina drew the segments shown. plain the error she made. (3) 9. Multiple hoice Which of the following statements is not true of a square? ll sides are congruent. The diagonals are congruent. The diagonals are perpendicular. The interior triangles created by the diagonals make two obtuse and two acute triangles. (5) Lesson

59 10. In this triangle, Z is tangent to at Z. etermine m Z. (58) 11. State the conjunction of these statements. Is the conjunction true or false? (0) The triangle is acute. The triangle has eactly two acute angles. 1. Find the value of and of y in the triangle shown. Give your answers in (56) simplified radical form. 58 Z 60 6 y 13. Generalize Line m is tangent to P at point. Points and are two other (58) distinct points on m. a. lassify P as acute, right, or obtuse when the order of,, and along line m is,,. b. lassify P when the order of,, and along line m is,,. c. an P ever be a right angle? Why or why not? 1. Find the lateral area of the prism shown. (59) 15 cm 36 cm 38 cm 15. onstruction Kai is trying to build a right triangle out of plastic to use as a brace (33) for furniture. fter constructing the brace, he measures its sides as 5.5 inches, 6.33 inches, and 8.5 inches. oes Kai need to cut more plastic off the hypotenuse, or does he need to find a longer piece to use for the hypotenuse? How do you know? 16. Find the volume of the right prism shown. (59) 5 ft 17. Model raw and label two similar polygons whose corresponding () sides have a ratio of 1:. 15 ft 15 ft 18. Using the diagram, find PU in terms of if PX = 8 and UY =. (38) Point P is the circumcenter of the triangle. Y 19. ccessibility ramp to the library makes a triangle (56) with the longer leg on the ground. If the ramp is 3 feet high, how long is the ramp s surface? X T P V U Z 0. Find the surface area of the prism shown. (59) y 1. lgebra Find the area and perimeter of the triangle formed by the (57) lines y =, y =, and y =. 5 in. 1 in.. Multi-Step Isosceles STU has base angles measuring 60 and a base (51) length of 1 foot, 7 inches long. etermine the perimeter of STU, in feet and inches. 6 in. 39 Saon Geometry

60 3. Water Treatment pipe with an 8-foot radius has water flowing through it, but (3) for safety reasons the water level must be kept at least.5 feet from the top of the pipe. If the water makes a chord that is 1.5 feet long, how close to the top of the pipe is the water flowing? Is the water at a safe level? 8 8. If a quadrilateral is inscribed in a circle, then its opposite angles (7) are. * 5. Write a two-column proof showing the first case of this theorem: (7) The measure of an inscribed angle is equal to half of the measure of its intercepted arc. Hint: raw X. Given: X is inscribed in X. Prove: m = 1 m X 6. plain why these two triangles are similar and give (6) a similarity statement. T W X Y 7. Find the height of a right rectangular prism whose surface area is 35 square (59) inches. The length of the base of the prism is 8 inches and the width of the base is inches. 8. Lawnmowing mma is mowing her neighbors lawns. mma (0) charges 1.5 cents per square foot of grass. How much should she charge to mow the lawn pictured here? Hint: mma does not mow the driveway. 9. Justify In two triangles, ST and WX, there are right angles at (18) and. a. If S W, what can be said about T and X? Justify your answer. b. If T X, what can be said about S and W? U V 8 ft 10 ft 50 ft 6 ft 5 ft 30. Identify the tangent line(s) in this figure. (58) l n m 5 Lesson

61 60 LSSON Proportionality Theorems Warm Up 1. Vocabulary Lines that lie in the same plane but never intersect are (5) called lines.. Rewrite this statement to make it true. Parallel and perpendicular lines have equal slopes. 3. Multiple hoice Which of the following is not true about the angles formed when a transversal intersects parallel lines? lternate interior angles are supplementary. lternate eterior angles are congruent. Same-side interior angles are supplementary. orresponding angles are congruent. (37) (3) New oncepts Previous lessons have discussed some of the proportional relationships that eist within triangles when they are divided by a midsegment. similar relationship eists for any line that intersects two sides of a triangle and is parallel to one side. Math Reasoning Formulate midsegment is parallel to one side of a triangle, so Theorem 60-1 applies. What is the ratio of the segments formed by the intersections of a midsegment with the triangle s sides? Theorem 60-1: Triangle Proportionality Theorem If a line parallel to one side of a triangle intersects the other two sides, it divides those sides proportionally. X_ Y = _ X Z ample 1 Using Triangle Proportionality to Find Unknowns a. Find the length of. _ = 5 = _ 3 = _ 10 3 Triangle Proportionality Theorem Substitute. Simplify. Y X 3 5 Z Online onnection b. Find the value of. Write a proportion relating the segments based on the Triangle Proportionality Theorem. L + 1 Z 5 N + 3 Y 10 M 396 Saon Geometry

62 _ + 1 = _ + 3 Triangle Proportionality Theorem ( + 1) = 5( + 3) ross multiply. = 1 Solve. The onverse of the Triangle Proportionality Theorem is true, and can be used to check whether a line that intersects sides of a triangle is parallel to the triangle s base. Theorem 60-: onverse of the Triangle Proportionality Theorem If a line divides two sides of a triangle proportionally, then it is parallel to the third side. In XYZ, if _ X Y = _ X, then YZ. Z X Y Z ample Proving Lines Parallel Is ST parallel to PR? If ST divides PQ and RQ proportionally, then ST PR T R by Theorem 60-. Set up a proportion. _ PS SQ = _ RT Triangle Proportionality Theorem TQ 3_ 8 =? _ Substitute. 7? 1 = 16 ross multiply. The statement is false, so ST is not parallel to PR. P 3 S 8 7 Q The Triangle Proportionality Theorem is closely related to Theorem 60-3, which uses the same proportional relationship to relate the segments of transversals that are intersected by parallel lines. Hint Theorem 60-3 Theorem 60-3 is very similar to the Triangle Proportionality Theorem. When and F meet, they will make a triangle with any segment of the parallel lines shown in the figure. If parallel lines intersect transversals, then they divide the transversals proportionally. _ = _ F F If parallel lines divide a transversal into congruent segments, then the segments are in a 1:1 ratio. y Theorem 60-3, any other transversal cut by the same parallel lines will be divided into segments that also have a 1:1 ratio, so they will also be congruent. Lesson

63 Theorem 60- If parallel lines cut congruent segments on one transversal, then they cut congruent segments on all transversals. In the diagram, if UV = VW, then XY = YZ. U X V Y W Z Math Reasoning onnect Parallel lines form many congruent and supplementary angles. From ample 3, name a pair of corresponding angles, and a pair of same-side interior angles. ample 3 Proving Theorem 60- Use a paragraph proof to prove Theorem 60-. Given:,, F Prove: F y Theorem 60-3, we know that = F. Since F, the ratio of to by substitution is the same as :, which is equal to 1. Substitute into the proportion given and obtain 1 =. Taking the cross product yields = F. y the F definition of congruent segments, F. Math Reasoning How is ample b related to Theorem 60-? ample Finding Segment Lengths with Intersecting Transversals a. Find the length of segment. The parallel lines cut F + 3 into congruent segments. Therefore, 3-1 is also cut into congruent segments. 3-1 = + 3 = = Substitute this value into the equation that gives. = + 3 = + 3 = 5 b. etermine whether UV, WX, and YX are U parallel when = W ecause VX = XZ, UW must equal WY 5-3. Y Z UW = - 1 = (3) - 1 = 11 WY = 5-3 = 5(3) - 3 = 1 UX WY. Therefore the lines UV, WX, and YZ are not parallel. F X 1 V Saon Geometry

64 Math Reasoning ample 5 pplication: rt Write How can you use perspective in everyday life to estimate the height of an object at a distance? Perspective is a method artists use to make an object appear as if it is receding into the distance. If the fence posts are parallel, then what is the length of if H =, =, = 6, and FH = 18? F G H Use Theorem 60-3 to write a proportion relating the segments given. H_ FH = 18 = _ ( + 6) = 1. Use the Segment ddition Postulate: = - - = =. Lesson Practice a. Find the length of. b. Find the length of PQ. ( 1) ( ) - 1 P Q R c. Use a paragraph proof to prove the Triangle Proportionality Theorem. Given: Prove: _ = _ d. Find the length of. e. etermine whether KL, MN, and OP are parallel. ( 3) ( ) ( ) K 3 F 1 M 13 L N P O ( 5) f. rt road is drawn with perspective. Find the length of if = 10, F = 0, and = 8. F Lesson

65 Practice istributed and Integrated 1. For parallelogram KLMN, prove the triangles congruent by SS ongruency. (8) N M y (38) y. lgebra Using the diagram, find WV in terms of if TW = 8, UV = 15, and TU = 5. T U K L 3. school is located at grid point (-1, ). If Jordan s home is on a street along the line y = 3-3, what is the shortest distance Jordan could possibly live from the school? () W V *. Fill in the blanks of the paragraph proof of the onverse of the (60) Triangle Proportionality Theorem: If a line divides two sides of a F triangle proportionally, then it is parallel to the third side. Given: = F, so F = F. Prove: F It is given that. y the Property of,, so F = F F by. y definition of similar triangles, F. Finally, by the, F. * 5. Multi-Step In PQR, P is a right angle. Find the perimeter of PQR to the (60) nearest tenth. * 6. right rectangular prism has a length, width, and height that are all equal. (59) The volume of the prism is 33 cubic meters. Find the surface area. P 5 X Y 6 R Q * 7. Write a paragraph proof of the Triangle ngle isector Theorem: If a line (31) bisects an angle of a triangle, then it divides the opposite side proportional to the other two sides of the triangle. Hint: raw X parallel to and etend to X. Given: In, bisects. Prove: _ = _ X 8. nalyze Find the measure of each angle in the inscribed quadrilateral. (7) N (8y + 8) 9. Sleep Patterns Unless edrick has at least eight hours of sleep per night, he is tired all day. This morning he woke early and did not get eight hours of sleep. What can we conclude about edrick today? (1) 10. Multi-Step Find the orthocenter of RTV with vertices (3) R(-, 6), T(1, 3), and V(7, 3). 11. rror nalysis This circle shown has center, and is a radius. (58) Mariah has calculated that in is 65. Why is her conclusion invalid? 1. Find the geometric mean of 33 and 7. (50) 5 M (7y) P (11y) Q 00 Saon Geometry

66 13. Multiple hoice Which set of side lengths could not form a triangle? (39), 5, 10 1,, 11, 15, 0 55, 1, 37 * 1. Find the surface area of the prism at right. (59) 15. Floor Refinishing Four congruent floors of a square office building need (53) to be refinished. The diagonal of one of the floors is 175 feet. If one can of refinisher covers 8000 square feet, how many cans are needed to finish the floors? * 16. Write re JK and LM parallel? plain how you know. L (60) J 8 7 M 11 in. 8 in. 5 in. K Verify is a midsegment of FGH. Find the coordinates of and. (55) Use the distance formula to verify that is a midsegment of FGH. * 18. Multiple hoice Which dimensions make PQ ST? (60) SR = 1, TR = 19 SR = 10, TR = 13.3 SR = 17.5, TR = 5 SR = 13, TR = 0 P Q 10 7 T S R O H(-, -) -8 y F(, 6) 8 G(, -) * 19. Find the volume of the oblique prism shown. (59) 0. Line l is tangent to at, and line m passes (58) through. Lines l and m intersect at. a. lassify by its angles. b. If m = 53, determine m. 16 m 19 m 10 m 8 m 1. Generalize Is every solid a polyhedron? plain. (9). There are just five regular polyhedra, sometimes called the Platonic solids after the Greek philosopher Plato. Which of these polyhedra does not have square or triangular faces, and what shape are its faces? (Inv 5) Tetrahedron faces ube 6 faces Octahedron 8 faces odecahedron 1 faces Icosahedron 0 faces Lesson 60 01

67 * 3. Justify Use an indirect proof to prove that an altitude of an equilateral triangle (8) is also a median. Given: is equilateral with altitude X. Prove: X is a median of.. Physics In an eperiment, wooden blocks with different masses are (16) attached to a force meter and dragged along a rough surface. This graph shows a line that models the results. What is the equation of this line? What are the correct units for the slope? 5. n octahedron is a regular polyhedron. If the bases of two congruent (9) square pyramids are glued together, the result is an octahedron. escribe the polygons that comprise the faces of an octahedron, and state the number of vertices, edges, and faces. 6. Find the value of and y in the triangle shown to the nearest tenth. (50) y 7 Force (newtons) y 6 8 Mass (kilograms) Geology Large meteor craters have been found that are nearly perfectly circular. (35) geologist is walking around one such crater. fter walking one mile, she finds that she has covered 85 degrees of arc. What is the radius of the crater, to the nearest foot? 8. Justify Find the value of in the figure, and justify your answer. (6) F 9. Formulate Write a formula that uses only the shorter leg to find the area of a (56) triangle. Let the shorter leg be equal to. 30. Traffic shop owner built his own stop sign according to the diagram. Find (57) the perimeter of the stop sign to the nearest unit. Is this a regular octagon? STOP 0 Saon Geometry

68 INVSTIGTION 6 Geometric Probability Math Reasoning Predict If it is 0% likely to rain on any of the net five days, how many days would you predict it to be rainy? Recall that the probability of an event happening is equal to the number of outcomes in which that event happens divided by the total number of possible outcomes. P (event) = Number of desired outcomes Number of possible outcomes perimental probability is a process where trials are conducted to test the probability of an event and the results are recorded. perimental probability is determined by dividing the number of trials where the desired event occurred by the total number of trials that were conducted. Geometric probability is a form of probability that is defined as a ratio of geometric measures such as lengths, areas, or volumes. For eample, a spinner that is divided into two congruent sections shaded red and blue has a 50% chance of landing on red. This is known because the red section makes up 50% of the spinner s area. If the red section comprised just 5% of the spinner s area, the chance that it would land on red would be 5%. In groups, assemble a spinner and conduct a probability eperiment. With a crayon or colored pencil, shade sectors 1-5 red. Shade sectors 6-7 blue. Shade sectors 8-10 yellow. ut a strip of paper or cardstock into the shape of an arrow, and fasten the arrow to the spinner base with a brad. 1. Use a protractor to measure the central angle of each of the three colored sectors of your spinner. What are the measures of the red, blue, and yellow central angles, respectively?. What percent of the time would you epect the spinner to land on red? Why? Math Reasoning onnect Why does the proportional area of the spinner sector give the theoretical probability? The probability of landing on red can be determined because it covers half the spinner. To determine the probability of landing on blue or yellow, write a proportion. For eample, blue measures 7 out of 360 in the entire circle. egrees in sector Total degrees in circle = _ = _ 1 5 s a percentage, this is 0%, so you would epect the spinner to land on blue about 0% of the time. Investigation 6 03

69 Now conduct a probability eperiment with the spinner. raw a table like the one shown. Include at least ten rows for results, with each row recording 10 spins in addition to the previous tallies brought down from the row above. Results perimental Probability Spins lue Yellow Red P(lue) P(Yellow) P(Red) 10 0 To fill out the first row of the table, spin the spinner 10 times and record a tally mark in the corresponding column for each time it lands on a color. Then, find the eperimental probability of landing on each color by dividing the number of times the spinner landed on the color by the total number of spins. Fill out the last three columns. Spin the spinner 10 more times and update the tallies for the net row of the table. ontinue finding the eperimental probability for each row until 100 spins have been tallied. 3. What are the theoretical probabilities of getting blue, yellow, and red?. How close are the eperimental probabilities in the first row of the table to the theoretical probabilities? How close are they in the fifth row of the table? 5. What trend occurs in the difference between the eperimental probabilities and the theoretical probabilities in the table as the number of spins increases? Math Reasoning Formulate If a pin is equally likely to be stuck anywhere in a square, what is the probability that it is stuck on the right side of the square? In the middle third? Suppose a plane figure P can be separated into nonoverlapping regions Q, R, and S. The theoretical probability for one of the smaller regions, say Q, is the ratio of the area of Q to the area of P. P(Q) = _ Q s long as an event that could happen in any region of P is random, the eperimental probability in a set of repeated trials should approach the theoretical probability. P Using graph paper, draw the shapes as shown in the art at right. olor each shape a different color. P(Q) = 3_ 7 ut each of the parallelograms and triangles 5 created by the gridlines. Place all of the 8 triangles in a bag. With all of the remaining parallelograms, cut each along a diagonal to make congruent triangles, and place these triangles in the bag with the others. raw a table like the one shown. Then randomly pull triangles from the bag and record the results in the table. 6 3 P Q 1 R 7 S 0 Saon Geometry

70 Shape Number of Triangles Theoretical Probability Shape _ 70 Shape 1 omplete the first column by listing the 8 shapes that made up the original figure. Make sure to note the color of each shape. In the second column, record the number of triangles that comprised each shape. In the third column, calculate the theoretical probability of drawing a part of each shape from the bag. egin taking shapes from the bag. Make a table to tally the results, as in the spinner eperiment. o as many trials as time allows. When finished, find the eperimental probability of drawing a triangle from each of the colored shapes. 6. ompare the eperimental probability to the theoretical probability. re the trends the same as in the spinner eperiment? 7. What is the theoretical probability that a triangle will be drawn that is part of Shape 1 or Shape? 8. ased on observations from both activities, what can be concluded about the eperimental and theoretical probabilities as more and more trials are conducted? Investigation Practice a. esign and make a spinner so that P(red) = 1_, P(blue) = 1_, and P(green) = 1_. b. onduct a probability eperiment with the spinner from part a. omment on the results. c. Use square grid paper to design a simple set of shapes that comprise a rectangle. Use only the grid lines as edges. Make a table like the one used in the second eperiment of this investigation for the set of shapes. d. Write a problem about the theoretical probabilities for the eperiment conducted in part c. change the probability problem with another student. Solve each other s problems. e. ompare your eperiment in part c with the eperiment in the second part of the investigation. In each activity, was the probability proportional to the number of triangles or squares in the shape, the area, or both? What key ideas about probability did you observe in both activities? Investigation 6 05