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**2-7-13 Equations to find missing angles **

Bring vocabulary folder and note cards to class on Friday. Equations to find missing angles EQ: How can you write and equation to find the measure of missing angles? 1. 2. 3. 4.

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Check Homework X = 30 X=50 x=-3

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x x+51=180 2x = 180 x= -7

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**Writing Equations to Find Missing Angles**

Unit 7 Math 7

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**Objective-To find missing angles using rules of geometry.**

Supplementary Angles- Angles whose sum is 180 . a b

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Find the value of x. x 30 x = 180 x = 150

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**Find the supplement of the given angle.**

1) 40 140 5) 89 91 2) 18 162 6) 23 157 3) 153 27 7) 131 49 4) 65 115 8) 118 62

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**Write a variable equation and solve.**

Find an angle whose supplement is 30 less than twice the angle. x 2x - 30 x + (2x - 30) = 180 3x - 30 = 180 3x = 210 70 x = 70

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**Complementary Angles sum is 90 . b a x+ 40 = 90 - 40 -40 x 40 x = 50**

- Angles whose sum is 90 . b a x+ 40 = 90 x 40 x = 50

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Find the complement of... 1) 20 70 2) 47 43 No complement 3) 100

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**Write a variable equation and solve.**

Find an angle whose complement is 20 more than three times the angle. x + 3x + 20 = 90 x 4x + 20 = 90 3x + 20 4x = 70 x = 17.5

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**angles of any triangle is always 180 . b**

180 Rule for Triangles - the sum of the interior angles of any triangle is always 180 . b 80 40 x a c x = 180 x = 180 x = 60

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Find each angle below. y + 14 = 63 2y - 10 2y - 10 = 88 y = 29 y+14 y - 20 180 (y + 14) + (2y - 10) + (y - 20) = 180 4y - 16 = 180 4y = 196 y = 49

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**Vertical Angles Theorem**

- the opposite angles of intersecting lines must be equal.

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**What’s the relationship between angles a and b?**

Vertical Angles Theorem - the opposite angles of intersecting lines must be equal. Find the missing angles a, b and c. What’s the relationship between angles a and b? 25 155 b c a 155 25

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Find the missing angle. x 40 48 132

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Summary: How can you write and equation to find the measure of missing angles? Homework: Vocabulary quiz on Friday; Handout; Test on Monday, Bring vocabulary folder and extra cards on Friday.

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