1. Angles: Setting up Equations

2. Right Angles Complementary angles: Set equation equal to 90. 3x+7
Add the two expressions.
(3x + 7) + (4x +13) = 90
7x + 20 = 90
7x = 70
x = 10
Combine like terms:
7x + 20 = 90
Solve for x:

3. Perpendicular Lines A AB __BC ABD = 7x+2 DBC = 5x+4 D 7x+2 5x+4 B C
Same as Complementary: adds to 90 degrees.
AB __BC
ABD = 7x+2
DBC = 5x+4
Set up the equation:
7x+2 + 5x+4 = 90
Combine Like Terms:
12x +6 = 90
Solve. D
7x+2
5x+4 B C

4. Supplementary Angles Supplementary Angles are along a straight line.
Add to 180 degrees.
5x+7
3x+13
Set up: x+7 + 3x+13= 180
Combine: x +20 =180
Solve:
Divide: x = 160
x = 20

5. Vertical Angles
With vertical angles, the ones across from each other are equal. E D
9x-4
7x+10 B
9x - 4 = 7x +10 A C
Variables on different sides of the equation.
9x – 4 = 7x + 10
-7x x
2x – 4 =
2x = 14
x= 7