1 Triangles Triangle A triangle is a closed figure in a plane consisting of three segments called sides. Any two sides intersect in exactly one point called a vertex. A triangle is named using the capital letters assigned to its vertices in a clockwise or counterclockwise direction. For example, the triangle below can be named triangle ABC in a counterclockwise direction starting with the vertex A. a. What are other names for triangle ABC? A triangle can be classified according to its sides, angles, or a combination of both. If a triangle has three congruent sides, it is called an equilateral triangle as shown below. A triangle with at least two sides congruent is called an isosceles triangle as shown below. b. Are all equilateral triangles isosceles? Why or why not? c. Are some isosceles triangles equilateral? Explain. Answers to questions a-c: a. Triangle ( ) ACB, BAC, BCA, CAB, CBA
2 b. All equilateral triangles are also isosceles triangles since every equilateral triangle has at least two of its sides congruent. c. Some isosceles triangles can be equilateral if all three sides are congruent. A triangle with no two of its sides congruent is called a scalene triangle and is shown below. Classification of Triangles by Sides Equilateral triangle: a triangle with three congruent sides Isosceles triangle: a triangle with at least two sides congruent Scalene triangle: a triangle with no two sides congruent Another way to classify triangles is according to their angles. A triangle with three acute angles can be classified as an acute triangle. A triangle with one obtuse angle can be classified as obtuse triangle.
3 A right triangle is a triangle with one right angle. Segments PQ and RP are called the legs of the right triangle and segment RQ is called the hypotenuse. The legs form the right angle RPQ. The side opposite the right angle is hypotenuse RQ. Classification of Triangles by Angles Acute triangle: a triangle with three acute angles Obtuse triangle: a triangle with one obtuse angle Right triangle: a triangle with one right angle Exercises True or False: Give a reason or counterexample to justify your response. 1. An equilateral triangle is always acute. 2. An obtuse triangle can also be isosceles. 3. The acute angles of a right triangle are complementary. 4. Use the figure below and find the value of x for each of the following.
4 a) AC= (x 2-2x+4) and BC= (x 2 +3x-11). b) BC= 17+3x and AC= x+25 c) AC= x 2-6x and BC= x Given ABC with vertices A(1,5), B(5,5), and C(5,1) a) graph ABC in the coordinate plane. b) classify this triangle by its sides and angles. Triangles can also be classified by using a combination of angle and side descriptors. Examples Right isosceles triangle Right scalene triangle Obtuse isosceles triangle
5 Exercises Complete each statement below with always, sometimes, or never and give a justification for your answer. 1. A scalene triangle is an acute triangle. 2. A right triangle is an obtuse triangle. 3. An isosceles triangle is a right triangle. 4. An equilateral triangle is an isosceles triangle. 5. The acute angles of a right triangle are supplementary. 6. A right isosceles triangle is equilateral.
6 Exploration Using linguine, snap off the ends to make segments 3, 5, 6, and 9 inches long. 1. Determine which sets of three lengths will make a triangle. 2. Which sets of three segments did not form a closed figure in the plane? 3. What do the sets that form a triangle have in common? Solution: 1. A triangle can be formed using the following sets of lengths: 3, 5, 6 5, 6, 9 2. The set consisting of 3, 6, and 9 did not form a triangle. 3+6=9 3. The sum of the lengths of any two sides of a triangle is greater than the length of the third side. This exploration leads to the following theorem: Triangle Inequality Theorem The sum of the lengths of any two sides of a triangle is greater than the length of the third side. Example 1. Two sides of a triangle have lengths of 4 cm and 7 cm. What are the possible lengths for the third side? 4 cm + 7 cm > x and 4 cm + x > 7 cm and 7 cm + x > 4 cm 11 cm > x and x > 3 cm and x > -3 cm The intersection of these inequalities can be represented graphically as the intersection of three rays with open endpoints as shown below.
7 All possible lengths of the third side are represented by the inequality 11cm > x > 3 cm. Exercises 1. The lengths of three segments are given. Determine if these segments can be used to form a triangle. a) 11 cm, 15 cm, and 23 cm b) 7.5 in, 8.3 in, and 4.2 in 2. The lengths of two sides of ABC are given as A=12 ft and BC=17 ft. What are the possible lengths of the third side AC? 3. DEF has side lengths as follows: DF=(x+1) m, DE=(3x-4) m, and EF= (x+7) m. What are the possible values of x? Segments of Triangles We will discuss three segments in a triangle: altitudes, medians, angle bisectors Definition An altitude of a triangle is the segment drawn from a vertex perpendicular to the opposite side or extension of that side.
8 Every triangle has three altitudes as shown in the figures below. Exploration In the previous drawings, it seems that the altitudes intersect in a common point. Investigate this idea by using paper folding with patty paper. a) Draw a large triangle on a sheet of patty paper. b) Cut out the triangle along its sides. c) Fold the altitudes of this triangle. d) The common point of intersection of these altitudes is called the orthocenter. Definition A median of a triangle is a segment having one endpoint at a vertex of a triangle and the other endpoint at the midpoint of the opposite side. A triangle also has three medians as shown in the diagram below. Exploration The medians in the drawing also seem to meet in a common point. Use patty paper and paper folding to verify this idea. a) Draw a large triangle on a sheet of patty paper. b) Cut out the triangle along its sides.
9 c) Crease each segment in the middle after matching its endpoints by folding the paper. This point that divides each segment into two congruent segments is called a midpoint. d) Make another fold connecting the midpoint of a side with the opposite vertex to form the median. Repeat this process for the other two sides. e) The point where all three medians intersect is called the centroid or center of mass. Definition An angle bisector of a triangle is the segment that bisects an angle of a triangle with one endpoint at the vertex of the angle bisected and the other endpoint on the opposite side of the triangle. Every triangle has three angle bisectors as shown in the figure below. Exploration We have medians and altitudes intersecting in a common point and it seems that the angle bisectors also have a common point of intersection. Use paper folding with patty paper to investigate this idea. a) Begin by drawing a large triangle on a sheet of patty paper. b) Use scissors to cut out the triangle along its sides. c) Hold an angle at its vertex and fold so that the sides meet along a line that includes the vertex. Continue this process and fold the other angle bisectors. d) The common point of intersection of these angle bisectors is called the incenter, the center of the inscribed circle in the triangle.
10 It has been shown that the altitudes, medians, and angle bisectors each have a common point of intersection called a point of concurrency. Examples 1. Given: DOT as shown Find the value of x so that AT is an altitude. 2. Given: PQR as shown PM = (3x- 8) in MR = (x + 5) in Find the value of x so that RM is a median. 3. Given: ANG as shown below m NAB = (5x 4) m GAB = (3x + 10) Find: x so that AB is the angle bisector of NAG
11 Solutions: 1. TA DO (Definition of an altitude) TAD is a right angle ( s form right angles) m TAD = 90 (Right s have a measure of 90.) 3x + 15 = 90 (Substitution) 3x = 75 (Subtraction property of equality) x = 25 (Division/multiplication property of equality) 2. PM = MR (Definition of a median) 3x 8 = x + 5 (Substitution) 2x = 13 (Addition property of equality) x = 6.5 (Division/multiplication property of equality) 3. m NAB = m GAB (Definition of an angle bisector) 5x 4 = 3x + 10 (Substitution) 2x = 14 (Addition property of equality) x = 7 (Division/multiplication property of equality) Exercises 1. Given: SWI 1 SM = ( x + 3) cm 2 2 MW = ( x 1) cm 3
12 Find: x so that IM is a median 2. Given: ABC m ABD = (5x 7.5) m CBD = (3x ) Find: x so that BD is an angle bisector 3. Given: CAN m ATN = (4x + 18) Find: x so that AT is an altitude
13 Congruent Triangles Exploration Cut pieces of linguine into lengths of 6 in, 8 in, and 10 in. 1. Use the pieces of linguine to form a triangle. 2. Is it possible to form a different triangle using these lengths? Explain. 3. How do these triangles compare? Solutions: 1. The pieces of linguine can be used to form the following triangle. 2. It is possible to form triangles with different orientations in the plane as shown below. Exploration 3. The triangles have the same size and shape as the original triangle shown. Use a piece of tracing or patty paper to trace the triangles in solution 2. Use rotations and translations to match corresponding sides. 1. How do the corresponding angles compare? 2. How many parts of one triangle match with corresponding parts of another triangle having the same size and shape? 3. What is the relationship between corresponding sides and corresponding angles in the set of triangles? Solutions: 1. The corresponding angles have the same measure. 2. Three sides and three angles of one triangle match with three corresponding sides and three corresponding angles of another triangle. 3. Corresponding sides are opposite corresponding angles. The triangles in solution 1 and solution 2 are said to be congruent.
14 Congruent Triangles Two triangles are congruent if and only if their corresponding sides and their corresponding angles are congruent. Examples 1. Given triangle ABC is congruent to triangle DEF. Identify the corresponding parts in the two triangles. Another way to state that triangle ABC is congruent to triangle DEF is by using the following notation: ABC DEF The corresponding sides and corresponding angles can be identified by matching the corresponding vertices of the two triangles as shown below. The corresponding sides and corresponding angles of two congruent triangles are referred to as corresponding parts of congruent triangles. We often write CPCTC for Corresponding Parts of Congruent Triangles are Congruent.
15 2. Show that the congruence of triangles is reflexive. Given: RST Show RST RST We know that RT RT, RS RS, and TS TS by the reflexive property of equality. R R, S S, and T T by the reflexive property of equality. We now have three sides and three angles of RST congruent to the three corresponding sides and corresponding angles of RST. By the definition of congruent triangles, RST RST. 3. Show that the congruence of triangles is transitive. Given: RST UVW, UVW XYZ Show RST XYZ We know that RS UV, RT UW, ST VW, R U, S V, and T W by CPCTC given RST UVW. Since UVW XYZ, we have UV XY, UW XZ, VW YZ, U X, V Y, and W Z by CPCTC. We know that congruent sides have equal measures and by the transitive property of equality we have the following: RS = XY, RT = XZ, and ST =YZ Using a similar justification, the following is true for corresponding angles: m R = m X, m S = m Y, and m T = m Z RST XYZ by definition of congruent triangles. 4. Congruence of triangles is also symmetric. This justification is left as an optional exercise.
16 Exercises 1. Given MNO PQR, identify the corresponding parts. 2. Given: MNO PQR, MN = (5x-11), PQ = (3x-2) Find: x and MN 3. Given: KLM NOP, m M = (5x + 23), and m P = (3x + 40) Find: x and m P 4. Given: ABC with vertices A(-3,2), B(2,6), and C(-3,6) and EFG with vertices E(2,2), F(7,-2), and G(2,-2) a) Find the lengths of each side and determine if the triangles are congruent. b) If the triangles are congruent, write a congruence statement for the two triangles. If the triangles are not congruent, justify your conclusion. Exploration By the definition of congruent triangles, two triangles are congruent if and only if the six parts of one triangle are congruent to the six corresponding parts of a second triangle. Is it possible for two triangles to be congruent using only some of the corresponding parts? If so, which corresponding parts are sufficient to show two triangles congruent? Do problem 1 in the activity Look Alikes using Cabri Junior on a TI-83+ graphing calculator. In this exploration, a triangle will be constructed using three sides of a given triangle. The results of this exploration leads us to the SSS congruence postulate for proving two triangles congruent. SSS Congruence Postulate Two triangles are congruent if and only if three sides of one triangle are congruent to three sides of a second triangle. Examples 1. Determine which of the following represents a pair of congruent triangles.
17 2. Given: ACB is isosceles, point M is the midpoint of AB Show AMC BMC. AC CB by the definition of an isosceles triangle. AM MB since M is the midpoint of AB. CM CM by the reflexive property of equality. Now we have AMC BMC by the SSS congruency postulate. 3. Given: RS VT, RT SV Prove: SRT TVS Statements Reasons 1. RS VT RT SV 2. ST ST 3. SRT TVS 4. SRT TVS 1. Given 2. Reflexive property of equality 3. SSS congruence postulate 4. CPCTC
18 Exercises 1. Given: MNO PQR Determine whether each statement is true or false and give a justification for your answer. a) MN PQ b) MNO PRQ c) m OMN = m QPR 2. Given: PQ SR PS QR Prove: PQS RSQ Complete the proof with an appropriate statement or reason. Statements 1. PQ SR PS QR PQS RSQ Reasons Transitive property of equality 3.
19 3. Given: AE BF EC DF AB CD Prove: AEC BFD Proof: Statements Reasons 1. AE BF EC DF AB CD 2. AE = BF, EC = DF, AB = CD AB + BC = CD + BC 5. AB + BC = AC, CD + BC = BD AEC BFD Reflexive property Substitution 7. SSS congruence postulate Given: RST with vertices R(-3,8), S(2,5), and T(2,8) MNP with vertices M(10,0), N(5,3), and P(5,0)
20 Show RST MNP. Exploration Refer to the activity Look Alikes in the Geometry Module. Use a TI-83+ graphing calculator with Cabri Junior and do problem 2. In this problem, a triangle will be constructed using two sides and the included angle of a given triangle. Side lengths and angle measures of the constructed triangle will be compared to the corresponding side lengths and angle measures of the original triangle. This activity refers to two sides and the included angle of a triangle. In the diagram below, the sides XZ and XY of XYZ are included in the sides of ZXY In the diagram below, the given sides (marked) are not included in the sides of ZXY. This diagram does not represent two sides and the included angle of a triangle. The results of this exploration lead us to the following congruence postulate for triangles.
21 SAS Congruence Postulate Two triangles are congruent if and only if two sides and the included angle of one triangle are congruent to two sides and the included angle of the second triangle. Examples 1. Which of the following represents a pair of congruent triangles? State the congruence postulate that applies and write a justification.
22 d) Given: AD and CE bisect each other at point O AOC DOE Solutions: 1. a) The triangles do not represent a pair of congruent triangles since the angle shown is not the included angle for the two sides given. b) The pair of triangles shown are congruent by the SAS congruence postulate since the sides marked are included in the sides of the right angle. c) RST RUT by the SAS congruence postulate as follows: S ST TU These corresponding sides are given. A STR RUT An angle bisector divides an angle into two congruent angles. S RT RT Reflexive property d) AOC DOE by the SAS and SSS congruence postulates. Using the SAS congruence postulate, we have the following justification: S CO EO A bisector of a segment divides it into two congruent segments. A AOC DOE Vertical angles are congruent. S AO DO A bisector of a segment divides it into two congruent segments. Using the SSS congruence postulate, we have the following justification: S AC DE Given S CO EO A bisector of a segment divides it into two congruent segments. S AO DO A bisector of a segment divides it into two congruent segments.
23 Examples 2. Given: AC BD CAB DBA Prove: AD BC Complete the following proof. Statements 1. AC BD CAB DBA AD BC Reasons Reflexive property 3. SAS congruence postulate Given: ABC with vertices A(-2,6), B(1,2), and C(1,8) DFE with vertices D(7,4), F(4,0), and E(4,6) BAC = FDE = 86.8 a) Graph the coordinates of the vertices of each triangle in the coordinate plane.
24 b) Determine if ABC DFE and state the congruence postulate used. 4. Given: KAR GTO with KA = (3x-10), GT = (x+2), m KAR = (5y-40) and m GTO = (3y-8) Find: x, y and KA Solutions: 2. Statements Reasons 1. AC BD CAB DBA 2. AB AB 3. CAB DBA 4. AD BC 1. Given 2. Reflexive property 3. SAS congruence postulate 4. CPCTC 3. b) The distance formula can be used to determine the distance between two points with coordinates (x, y) and (x 1,y 1 ) in the coordinate plane: d = ( x x y ) + ( y 1) Using the distance formula above, the following lengths of sides can be determined. AC = AB = ED = ( ) + (6 8) = ( ) + (6 2) = ( ) + (6 4) = ( 2 2 3) + ( 2) = 4 ( ) 4 = 16 ( ) 2 = = = 25 = = 13
25 DF = ( ) + (4 0) = = = 25 = 5 Exercises We now have AC DE and AB DF since congruent segments have equal measures. BAC and FDE have the same measure and are also congruent. This gives us two sides and an included angle of ABC congruent to two sides and an included angle of DFE. Therefore, ABC DFE by the SAS congruence postulate. 4. We have KA = GT from the congruence statement. This allows us to write and solve the following equation: 3x -10 = x + 2 2x = 12 x = 6 To find KA, substitute the value 6 for x in the equation KA = (3x-10) and get KA = (3 6-10) = 8. Since corresponding angles of congruent triangles are congruent, m KAR = m GTO. By substituting the algebraic expressions for these measures, we have the following equation: 5y-40 = 3y-8 Solve this equation for y : 2y = 32 y = Given: AC BC CD CE Prove: A B
26 Complete the following proof. Statements Reasons Given ACE BCD Reflexive property CPCTC 2. Given: ACB is isosceles with base AB ray CD bisects ACB Show ADB is isosceles Write a justification explaining why ADB is isosceles. This justification may be written in the two-column format like the proof in exercise 1 or in a paragraph format. 3. Given: PQR with vertices P(-3,1), Q(1,1), and R(1,6) STU with vertices S(8,2), T(4,2), and U(4,7) a) Graph the triangles in the coordinate plane. b) Determine if PQR and STU are congruent. c) Justify your answer. 4. Given: Right triangle ACB with right ACB Right triangle DEF with right DEF AC DE and BC EF Prove: ACB DEF This proof leads to the following theorem for proving right triangles congruent.
27 Leg-Leg Theorem If two legs of one right triangle are congruent to two legs of a second right triangle, then the right triangles are congruent. 5. Given: Circle O with radii OG and OH OM bisects GOH GM = x 2 + 2x + 5 HM = x 2 + x + 11 OM = 3x 6 Find: x, GH, and OM Exploration Refer to the activity Look Alikes in the Geometry Module. Use a TI-83+ graphing calculator with Cabri Junior and do problem 3. In this problem, a triangle will be constructed using two angles and the included side of a given triangle. Angle measures and side lengths of the constructed triangle will be compared to the corresponding angle measures and side lengths of the original triangle. This activity refers to two angles and the included side of a triangle. In the diagram below, HI is the included side between H and I.
28 The results of this exploration lead us to the following congruence postulate for triangles. ASA Congruence Postulate Two triangles are congruent if and only if two angles and the included side of one triangle are congruent to two angles and the included side of a second triangle. Examples 1. Which of the following pairs of triangles are congruent by the ASA congruence postulate? Justify your reasoning. 2. Given: CD bisects ACB CD AB
29 Prove: ACB is isosceles using a flow-chart proof. 3. Given: ADB CBD ABD CDB m A = 3x + 15 m C = 8x 20 Find: x and m A Solutions: 1. a) CAM DBM by the ASA congruence postulate. A A B (Right angles are congruent.) S AM MB (A midpoint divides a segment into two congruent segments.) A AMC BMD (Given) b) WOX ZOY by the SAS congruence postulate. The ASA congruence postulate does not apply to this problem. S XO YO (A bisector divides a segment into two congruent segments.)
30 A XOW YOZ (Vertical angles are congruent.) S WO OZ (A bisector divides a segment into two congruent segments.) 2. A flow-chart proof shows the logical development of a proof using statements with supporting justification(s) in a flow-chart format. The statements and reasons are shown in rectangles with arrows indicating how they connect to other information in rectangles. The flow of information should lead to the conclusion. The proof that follows models one format that can be used. CD bisects ACB Given ACD BCD Definition of an angle bisector CD CD Reflexive ADC BDC ASA postulate AC BC CPCTC ACB is isosceles Definition of an isosceles CD AB Given ADC and BDC are right angles s form rt. s ADC BDC All right s 3. ADB CBD by the ASA congruence postulate. A ADB CBD (Given) S DB DB (Reflexive property) A ABD CDB (Given) A C (CPCTC) m A = m C (Congruent angles have equal measures.) 3x+15 = 8x-20 (Substitution) 35 = 5x (Addition and subtraction properties of equality) 7 = x (Division property of equality) m A = 3x + 15 = = = 36
31 Exercises 1. Given: AD bisects BC AB BC DC BC Prove: BC bisects AD Proof: Complete the proof below. 1. AD bisects BC AB BC DC BC Statements 2. B and C are right angles BE BC 5. AEB DEC BC bisects AD Reasons All right angles are congruent ASA congruence postulate 7. CPCTC 8.
32 2. Given: YVW is isosceles with base VW UYV XYW UVY XWY Prove U X using a flow-chart proof. 3. Given: BAC DCA AE EC DC = (x 2 + 2x 1) cm AB = (x 2 + 5x 7) cm Find: x and AB 4. Given: M R MI RI m RPI = (9x 10) m MQI = (4x + 45)
33 Find: x and m MQI We have explored the SSS, SAS, and ASA congruence postulates and LL theorem (right triangles only). Are there other ways to show two triangles congruent? We will consider the possibility of using any two angles and a side (not included) of one triangle (AAS) congruent to the corresponding parts of another triangle in the following proof. Given: HIJ and KLM H K, J M HI KL Prove: HIJ KLM
34 Proof: HIJ and KLM Given H K Given J M Given I L If 2 s of one 2 s of a second, 3 rd s are. HIJ KLM ASA congruence postulate HI KL Given This proof leads to the following theorem for showing two triangles congruent. AAS Congruence Theorem If two angles and a side (not included) are congruent to the corresponding parts of a second triangle, then the two triangles are congruent. Exploration Is it possible for two triangles to be congruent using SSA where the angle is not included between the two sides? Make a conjecture:. This conjecture will be tested in the following exploration. Given: Two segments and a non-included angle
35 Patty paper, a compass, and straight edge will be needed for this exploration. Follow the procedure outlined below. a) Trace the longer segment given ( AB ) on a sheet of patty paper. b) Place the patty paper over the given angle and align the vertex of the angle with endpoint A of the longer segment. Align one of the sides of the angle with AB. c) Trace the angle and extend the side not aligned with the segment as shown below. d) Construct circle B with a radius equal to the length of the shorter segment given. ( The construction below is not drawn to scale.) Circle B intersects ray AD in two points, point C and point D. There are two possible triangles that can be constructed with the given CAB, AB, and the shorter segment represented by the radii BC and BD. ABC and ABD are the two triangles shown in the figure above. Therefore, it is not possible to construct a unique triangle given two sides and a non-included angle.
36 Examples 1. Given: CED is isosceles with base CD GB AD CF GE CH = ED CE = AG A FEC GBF CFB Identify all pairs of congruent triangles in the figure given and explain the congruence postulate or theorem used. 2. Given: 1 2 DB AC Prove: DB bisects ADC
37 Write a paragraph, two-column, or flow-chart proof. 3. Given: DBE is isosceles with base DE A C ABE CBD AB = ( 2 1 x + 1) cm BC = ( 4 3 x 5) cm Find: x, AB, and BC Solutions: 1. ABG EFC by the AAS congruence theorem A A FEC (Given) A ABG EFC ( s form rt. s and all rt. s ) S AG CE (CE=ED=AG; seg. have = meas.) CDE CDH by the SSS congruence postulate S CH DE (Given; seg. have = meas.) S CE DH (CE=ED=CH=DH; seg. have = meas.) S CD CD (Reflexive property) GBF CFB by the SAS congruence postulate S GB CF ( ABG EFC; CPCTC)
38 A GBF CFB (Given) S BF BF (Reflexive property) 2. Triangle ABD will be shown congruent to triangle CBD using the AAS congruence theorem in a paragraph-style proof as follows. Angle 1 is congruent to DAB and 2 is congruent to DCB because vertical angles are congruent. Angle DBA and DBC are right angles since DB AC. It follows that DBA DBC because all right angles are congruent. Side DB is congruent to itself by the reflexive property. We now have ADB CDB by the AAS congruence theorem. Angle ADB is congruent to CDB by CPCTC. Therefore, DB bisects ADC. 3. ABE CBD by AAS A A C (Given) A ABE CBD (Given) S BE BD (An isosceles triangle has 2 congruent sides.) AB BC (CPCTC) AB = BC (Congruent segments have equal measures.) 1 3 x + 1 = x (Substitution) 6 = 4 1 x 24 = x AB = = 13 cm CD = AB = 13 cm Exercises 1. Given: BAE DBA DB AE a) Identify all pairs of congruent triangles in the given figure. b) Explain the congruence postulate or theorem used.
39 2. Given: RVS USV RSV UVS WRV TUS W T VW = ( 3 2 x + 3) in ST = ( 6 5 x 1) in RS = ( 2 1 x + 5) in 3. Given: Isosceles ABC with base AB CD bisects the vertex angle Prove: CD is a median to the base. Write a paragraph, two-column, or flow-chart proof.
40 This proof leads to the following theorem for isosceles triangles. Isosceles Triangle Theorem The bisector of the vertex angle of an isosceles triangle is the same segment as the median to the base. 4. Given: FRD with vertices F(-4,1), R(-1,3), and D(-3,5) TSU with vertices T(1,1), S(4,3), and U(2,5) F T and D U a) Graph each triangle in the coordinate plane. b) Show FRD TSU.
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Intermediate Math Circles October 10, 2012 Geometry I: Angles Over the next four weeks, we will look at several geometry topics. Some of the topics may be familiar to you while others, for most of you,
CHAPTER 8 QUADRILATERALS (A) Main Concepts and Results Sides, Angles and diagonals of a quadrilateral; Different types of quadrilaterals: Trapezium, parallelogram, rectangle, rhombus and square. Sum of
Class: Date: Geo, Chap 4 Practice Test, EV Ver 1 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. (4-3) In each pair of triangles, parts are congruent as
Mathematics 3301-001 Spring 2015 Dr. Alexandra Shlapentokh Guide #3 The problems in bold are the problems for Test #3. As before, you are allowed to use statements above and all postulates in the proofs
Unit 8: Congruent and Similar Triangles Lesson 8.1 Apply Congruence and Triangles Lesson 4.2 from textbook Objectives Identify congruent figures and corresponding parts of closed plane figures. Prove that
MATH 206 - Midterm Exam 2 Practice Exam Solutions 1. Show two rays in the same plane that intersect at more than one point. Rays AB and BA intersect at all points from A to B. 2. If C is the midpoint of
Chapter H2 Equation of a Line The Gradient of a Line The gradient of a line is simpl a measure of how steep the line is. It is defined as follows :- gradient = vertical horizontal horizontal A B vertical
Definitions, s and s Name: Definitions Complementary Angles Two angles whose measures have a sum of 90 o Supplementary Angles Two angles whose measures have a sum of 180 o A statement that can be proven
Key Terms for This Session Session 5 Dissections and Proof Previously Introduced midline parallelogram quadrilateral rectangle side-angle-side (SAS) congruence square trapezoid vertex New in This Session
GEOMETRY The University of the State of New York REGENTS HIGH SCHOOL EXAMINATION GEOMETRY Thursday, August 13, 2009 8:30 to 11:30 a.m., only Student Name: School Name: Print your name and the name of your
Chapter 3 Foundations of Geometry 2 3.1 Triangles, Congruence Relations, SAS Hypothesis Definition 3.1 A triangle is the union of three segments ( called its side), whose end points (called its vertices)
Visualizing Triangle Centers Using Geogebra Sanjay Gulati Shri Shankaracharya Vidyalaya, Hudco, Bhilai India http://mathematicsbhilai.blogspot.com/ firstname.lastname@example.org ABSTRACT. In this paper, we will
CONDENSED LESSON 3.1 Duplicating Segments and ngles In this lesson, you Learn what it means to create a geometric construction Duplicate a segment by using a straightedge and a compass and by using patty
of 9 1/28/2013 8:32 PM Teacher: Mr. Sime Name: 2 What is the slope of the graph of the equation y = 2x? 5. 2 If the ratio of the measures of corresponding sides of two similar triangles is 4:9, then the
/27 Intro to Geometry Review 1. An acute has a measure of. 2. A right has a measure of. 3. An obtuse has a measure of. 13. Two supplementary angles are in ratio 11:7. Find the measure of each. 14. In the
Final Review Geometry Fall Semester Multiple Response Identify one or more choices that best complete the statement or answer the question. 1. Which graph shows a triangle and its reflection image over
CHAPTER Vocabulary The table contains important vocabulary terms from Chapter. As you work through the chapter, fill in the page number, definition, and a clarifying example. biconditional statement conclusion
Name: Class: Date: ID: A Geometry Module 4 Unit 2 Practice Exam Multiple Choice Identify the choice that best completes the statement or answers the question. 1. Which diagram shows the most useful positioning
Review the Geometry sample year-long scope and sequence associated with this unit plan. Mathematics Possible time frame: Unit 1: Introduction to Geometric Concepts, Construction, and Proof 14 days This
Quadrilaterals / Mathematics Unit: 11 Lesson: 01 Duration: 7 days Lesson Synopsis: In this lesson students explore properties of quadrilaterals in a variety of ways including concrete modeling, patty paper
Conjectures for Geometry for Math 70 By I. L. Tse Chapter Conjectures 1. Linear Pair Conjecture: If two angles form a linear pair, then the measure of the angles add up to 180. Vertical Angle Conjecture:
Geometry Unit 5 Relationships in Triangles Name: 1 Geometry Chapter 5 Relationships in Triangles ***In order to get full credit for your assignments they must me done on time and you must SHOW ALL WORK.
47 Similar Triangles An overhead projector forms an image on the screen which has the same shape as the image on the transparency but with the size altered. Two figures that have the same shape but not
5-1 Perpendicular and Angle Bisectors Equidistant Distance and Perpendicular Bisectors Theorem Hypothesis Conclusion Perpendicular Bisector Theorem Converse of the Perp. Bisector Theorem Locus Applying
ANALYTIC GEOMETRY Study Guide Georgia End-Of-Course Tests TABLE OF CONTENTS INTRODUCTION...5 HOW TO USE THE STUDY GUIDE...6 OVERVIEW OF THE EOCT...8 PREPARING FOR THE EOCT...9 Study Skills...9 Time Management...10
1.1 Identify Points, Lines, and Planes Objective: Name and sketch geometric figures. Key Vocabulary Undefined terms - These words do not have formal definitions, but there is agreement aboutwhat they mean.
1. Given: a b, b c a c Guidance: Draw a line which intersects with all three lines. 2. Given: a b, c a a. c b b. Given: d b d c 3. Given: a c, b d a. α = β b. Given: e and f bisect angles α and β respectively.
summary of definitions, postulates, algebra rules, and theorems that are often used in geometry proofs: efinitions: efinition of mid-point and segment bisector M If a line intersects another line segment
Chapter 6 Notes: Circles IMPORTANT TERMS AND DEFINITIONS A circle is the set of all points in a plane that are at a fixed distance from a given point known as the center of the circle. Any line segment
Circles, Chords, Diameters, and Their Relationships Student Outcomes Identify the relationships between the diameters of a circle and other chords of the circle. Lesson Notes Students are asked to construct
Geometry Chapter 1 Section Term 1.1 Point (pt) Definition A location. It is drawn as a dot, and named with a capital letter. It has no shape or size. undefined term 1.1 Line A line is made up of points
Chapter 9 Circles Objectives A. Recognize and apply terms relating to circles. B. Properly use and interpret the symbols for the terms and concepts in this chapter. C. Appropriately apply the postulates,
1 Find the length of BC in the following triangles It will help to first find the length of the segment marked X a: b: Given: the diagonals of parallelogram ABCD meet at point O The altitude OE divides
The Use of Dynamic Geometry Software in the Teaching and Learning of Geometry through Transformations Dynamic geometry technology should be used to maximize student learning in geometry. Such technology
GEOMETRY Constructions OBJECTIVE #: G.CO.12 OBJECTIVE Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic
Given: ABC CD bisects AB CD AB Prove: ACD BCD 1. ABC CD bisects AB CD AB 2. AD DB Side 3. CDA and CDB are right 4. CDA CDB Angle 5. CD CD Side 6. ACD BCD 2. A bisector cuts a segment into 2 parts. 3. lines
Chapters 6 and 7 Notes: Circles, Locus and Concurrence IMPORTANT TERMS AND DEFINITIONS A circle is the set of all points in a plane that are at a fixed distance from a given point known as the center of
IMO Geomety Problems (IMO 1999/1) Determine all finite sets S of at least three points in the plane which satisfy the following condition: for any two distinct points A and B in S, the perpendicular bisector
Name: Class: Date: ID: A Geometry First Semester Final Exam Review Multiple Choice Identify the choice that best completes the statement or answers the question. 1. Find m 1 in the figure below. PQ parallel.
Math 531, Exam 1 Information. 9/21/11, LC 310, 9:05-9:55. Exam 1 will be based on: Sections 1A - 1F. The corresponding assigned homework problems (see http://www.math.sc.edu/ boylan/sccourses/531fa11/531.html)
Class: Date: Geometry EOC Practice Test #4 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. In the diagram below, which expression represents x, the degree
GEOMETRY (COMMON CORE) The University of the State of New York REGENTS HIGH SCHOOL EXAMINATION GEOMETRY (Common Core) Tuesday, June 2, 2015 1:15 to 4:15 p.m., only Student Name: School Name: The possession
Class: Date: Geometry EOC Practice Test #2 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. Rebecca is loading medical supply boxes into a crate. Each supply
2006 Geometry Form Page 1 1. he hypotenuse of a right triangle is 12" long, and one of the acute angles measures 30 degrees. he length of the shorter leg must be: () 4 3 inches () 6 3 inches () 5 inches
Geometry: Unit 1 Vocabulary 1.1 Undefined terms Cannot be defined by using other figures. Point A specific location. It has no dimension and is represented by a dot. Line Plane A connected straight path.
GLOSSARY Appendix A Appendix A: Glossary Acute Angle An angle that measures less than 90. Acute Triangle Alternate Angles A triangle that has three acute angles. Angles that are between parallel lines,
GPS GEOMETRY Study Guide Georgia End-Of-Course Tests TABLE OF CONTENTS INTRODUCTION...5 HOW TO USE THE STUDY GUIDE...6 OVERVIEW OF THE EOCT...8 PREPARING FOR THE EOCT...9 Study Skills...9 Time Management...10
Playing with bisectors Yesterday we learned some properties of perpendicular bisectors of the sides of triangles, and of triangle angle bisectors. Today we are going to use those skills to construct special
Mathematical Sentence - a sentence that states a fact or complete idea Open sentence contains a variable Closed sentence can be judged either true or false Truth value true/false Negation not (~) * Statement
130 Mathematics 19 Angles in a Circle and Cyclic Quadrilateral 19.1 INTRODUCTION You must have measured the angles between two straight lines, let us now study the angles made by arcs and chords in a circle
GEOMETRY The University of the State of New Yk REGENTS HIGH SCHOOL EXAMINATION GEOMETRY Thursday, June 17, 2010 1:15 to 4:15 p.m., only Student Name: School Name: Print your name and the name of your school
CHAPTER 6 LINES AND ANGLES 6.1 Introduction In Chapter 5, you have studied that a minimum of two points are required to draw a line. You have also studied some axioms and, with the help of these axioms,
Heron s Formula Lesson Summary: Students will investigate the Heron s formula for finding the area of a triangle. The lab has students find the area using three different methods: Heron s, the basic formula,
Chapter Additional Topics in Math In addition to the questions in Heart of Algebra, Problem Solving and Data Analysis, and Passport to Advanced Math, the SAT Math Test includes several questions that are
Geometry Semester 1 Review Part 2 Name Show all work for credit. Attach paper as needed to keep work neat & organized. Determine the reflectional (# of lines and draw them in) and rotational symmetry (order