12.1 Complementary and Supplementary Angles

Homework: p689, #12-22 even

Key Terms Complementary Angles:

__________________________________

Supplementary Angles: __________________________________

Complement: __________________________________

Supplement:__________________________

_____________________________

Two angles that add to equal 90°

Two angles that add to equal 180°

To find a complement, subtract the given measure from 90°

To find a supplement, subtract the given measure from 180°

Example 1: Identify Complements and Supplements

Determine whether the angles are complementary, supplementary, or neither.

1. m1 = 48°m2 = 42°

2. m3 = 125°m4 = 55°

Checkpoint Determine whether the angles are

complementary, supplementary, or neither.

1. m1 = 63°m2 = 27°

2. m3 = 146°m4 = 44°

3. m5 = 95°m6 = 85°

Keywords

Adjacent angles : _______________________________________________________________________

Example:

Two angles that share the same side

Example 2: Identify Adjacent Angles

List the numbered angles that are adjacent and then list the nonadjacent angles.

Adjacent Angles Non-adjacent Angles

Example 3: Measures of Complements and Supplements

a.) A is a complement of C, and m A=47°. Find m C

b.) P is a supplement of R, and m R=36°. Find m P.

Checkpoint

4.) B is a complement of D, and mD=79°. Find mB

5.) G is a supplement of H, and mG=115°. Find mH.

Closure

Describe what complementary angles are.

Describe what supplementary angles are.

Connection to Algebra

Find the value of x in the figure. Then find the unknown angle measures.

1. 3.2.