Notes: Special Pairs of Angles

Congruent Angles: Angles of equal measure.

Vertical Angles: Angles opposite each other when 2 lines intersect. Vertical angles are congruent. a b d c m a = m c m b = m d (“measure of angle b equals the measure of angle d”)

Bisector: Cuts an angle into 2 equal parts.

45˚ 45˚ Bisector

Adjacent angles: Angles that have the same vertex and share a side but do not overlap.

● D C● ● B

A●  CAB is adjacent to  DAC

Complementary Angles: 2 angles whose sum is 90 degrees. Example: A 40˚ degree angle and a 50˚ angle are complementary. (They do not need to be adjacent)

Supplementary Angles: 2 angles whose sum is 180 degrees. Example: A 160˚ angle and a 20˚ angle are supplementary. (Do not need to be adjacent) Practice with Special Angle Pairs Use this diagram for questions 1,2,3:

1) How many degrees are in angle ABC? ______

2) How many degrees are in angle ABD if angle DBC is 15°? ______

3) Angle ABD and Angle DBC are called ______angles.

Use this diagram for questions 4-7: 1 4 2 3

4) What is the relationship between angles 1 and 2? ______and

they are also ______

5) What is the relationship between angles 1 and 4? ______and

they are also ______

6) What is true about angles 2 and 4? ______

7) If angle 1 measures 125 degrees:

Find m 2 ______

Find m 3 ______

Find m 4 ______