Writing Equations to Find Missing Angles Unit 7 Math 7

Objective-To find missing angles using rules of geometry. Supplementary Angles- Angles whose sum is 180 . a b

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

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

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 +30 +30 3x = 210 70 x = 70

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 - 40 -40 x 40 x = 50

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

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 - 20 -20 4x = 70 4 4 x = 17.5

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 40 + 80 + x = 180 120 + x = 180 x = 60

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

Vertical Angles Theorem - the opposite angles of intersecting lines must be equal.

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

Find the missing angle. x 40 48 132