PERIMETERS A perimeter is the measure of the distance AROUND an object. Triangles

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1 PERIMETERS perimeter is the measure of the distance ROUND an object. S l S S w w S Perimeter of a Square = S +S+ S + S = 4S Scalene Triangle l 1 l 2 Triangles l Perimeter of a Rectangle = w + l + w + l = 2w + 2l Isosceles Triangle (2 sides and 2 angles are equal) l 3 Perimeter of a Scalene Triangle = l 1 + l 2 + l 3 Equilateral Triangle (3 sides and 3 angles are equal) s s s = = = = = Perimeter of an Equilateral Triangle = s + s + s = 3s s s t S== = s Perimeter of an Isoceles Triangle = s + s + t = 2s + t

2 Example: The perimeter of a rectangle is 26 ft. The length of the rectangle is 1 ft more than twice the width. Find the width and length of the rectangle. Step 1) What are we trying to find? The width and length of the rectangle. Let w = width, and l = length. Given info: Perimeter is 26 ft. It is a rectangle, so the formula for a rectangle s perimeter is P = 2w + 2l. lso, length of the rectangle is 1 ft more than twice the width. Step 2) Make an equation from given info. Perimeter = 26 ft = 2w + 2l Length is 1 ft more than twice its width. l = 1 + 2w We can combine these equations to solve for each variable, w and l. 26 = 2w + 2l Substitute equation, l = 1 + 2w for l in the above equation. 26 = 2w + 2(1 + 2w) Step 3) Solve equation Use distributive property to get rid of parentheses. 26 = 2w w ombine like terms 26 = 6w = 6w 4 = w What about l? l = 1 + 2w = 1 + 2(4) = 1+8=9 Step 4) heck result. Perimeter with w=4 and l=9 should be = 2(4) + 2(9)= = 26 Yes. Step 5) State conclusion (Remember the measuring units!) The width of the rectangle is 4 ft and the length is 9 ft.

3 Example 1 The perimeter of an isosceles triangle is 25 ft. The length of the third side is 2 ft less than the length of one of the equal sides. Find the measures of the three sides of the triangle. Now you try this one: carpenter is designing a square patio with a perimeter of 52 ft. What is the length of each side?

4 ngles are formed by two rays, lines, or line segments with a common endpoint. The common endpoint is called the vertex. In the angle below, point is the vertex. The angle can be denoted as or Note that the vertex, point, must be in the middle. vertex The unit of measurement of an angle is degrees. Right angle 90 cute angle Less than 90 Obtuse angle Greater than 90 Straight angle 180

5 Intersection Point E D Intersecting lines form angles at their intersection point. ngles that share a common side are called adjacent angles. The angles that are not adjacent are called vertical angles. E and and ED and are adjacent angles. D are adjacent angles. are vertical angles. Vertical angles have equal measures of degrees. We call this being congruent. Example The vertical angles property allows us to make an equation: 3x+15 = 4x -20 and solve for x. (3x+15) (4x-20) Two angles are supplementary angles when the sum of their measures is 180. When two lines intersect, adjacent angles are supplementary because the sides that are not in common form a straight angle. ED and D are supplementary angles. ED + D = Two angles are complementary angles when the sum of their measures is 90. When two adjacent angles form a right angle with the sides that are not in common, these angles are complementary because the measures add up to 90. D and D are complementary angles.

6 Parallel lines are lines in the same plane that never intersect (that have the same slope). If two lines, l 1 and l 2 are parallel, we say l 1 l 2. Transversal a line that intersects two or more lines on the same plane. E G D F H lternate Interior ngle Property transversal intersects parallel lines at congruent angles. ecause of this and also because of the property of supplementary angles and the property of vertical angles, we can rewrite the diagram on the left as this: The angles on the inside of the parallel lines that are congruent are called lternate Interior ngles. = and D = D and F F are alternate interior angles. E E are alternate interior angles

7 Example Given that l 1 l 2, solve for x l 1 (3x+20) These two angles are not equal, but we can still solve for x by using other properties. l 2 (3x-80) l 1 (3x-80) (3x+20) Since these two lines are parallel, the transveral intersects them at congruent angles, so the angle adjacent to (3x+20) is (3x-80). l 2 (3x-80) The supplementary angle property says that if two adjacent angles form a straight angle with uncommon sides, they are supplementary, so (3x 80) + (3x + 20) = 180. Now that we have an equation, we can solve for x.

8 The Sum of the Measures of the Interior ngles of a Triangle is 180 The sum of angles in a triangle is always 180 degrees. rigorous proof takes some work, but the statement can be made plausible by the following argument. In the triangle, draw a line through point that is parallel to. This creates two additional angles, ' and '. The three angles (',,') add up to 180 degrees, because they are adjacent to each other and backed off against a straight line. However, by the properties of parallel lines, ngle = ngle ' and ngle = ngle '. Therefore (,,) also add up to 180 degrees. l 1 l 1 l 2 l 2

9 Example 5: Given that ngle a = 45 and ngle x = 100, find the measure of angles b,c, and y. x b c y l a k ngle b = ngle c = ngle y =

10 Try this one: Given that ngle y = 55, and that lines m and k are perpendicular. find the measures of angles a, b, and d. m d b k a y ngle a = ngle b = ngle d =

11 hapter 4. 4 Markup and Discount $ Retail Price = $ost + $ Markup Selling price for an item mount the store paid for the item Markup = Markup Rate * $ost $ Sale Price= $ Original Price $ Discount $Discount = Discount Rate * $Original Price mount the store raises the price to make a profit Markup rate must be converted from percent to decimal before multiplying. Original Price is the Regular Price of the item. Example The manager of a clothing store buys a suit for $180 and sells that suit for $252. Find the markup rate. $Markup = Markup Rate * $ost So Markup Rate = $Markup/ $ost We know the cost of the suit, that is $180. What is the Markup? We can use the other formula, $Retail Price = $ost + $Markup to find Markup. $Markup = $Retail Price - $ost = $252 - $180 = $72 Markup Rate = $Markup/ $ost = $72/$180 = 0.4 onverting 0.4 to percent, we get 40%. onclusion: Markup Rate is 40% You try this: The cost to a sporting goods store of a tennis racket is $120. The selling price of the racket is $180. What is the markup rate?