### Complementary Angles

Two angles are **complementary** when they add up to . Complementary angles do not have to be congruent to each other, nor do they have to be next to each other.

#### Measuring Complementary Angles

1. The two angles below are complementary. . What is ?

Because the two angles are complementary, they add up to . Make an equation.

2. The two angles below are complementary. Find the measure of each angle.

Again, the two angles add up to . Make an equation.

However, this is not what the question asks for. You need to plug back into each expression to find each angle.

For : , so .

For : , so .

#### Identifying Complementary Angles

Name one pair of complementary angles in the diagram below.

One example is and .

### Examples

Find the measure of an angle that is complementary to if is

#### Example 1

#### =

#### Example 2

=

#### Example 3

=

#### Example 4

=

### Review

Find the measure of an angle that is complementary to if is:

Use the diagram below for exercises 8-9. Note that .

- If , find .
- If , find .

For 10-15, determine if the statement is true or false.

- Complementary angles add up to .
- Complementary angles are always .
- Complementary angles are always next to each other.
- Complementary angles add up to .
- Two angles that make a right angle are complementary.
- The two non-right angles in a right triangle are complementary.

### Review (Answers)

To view the Review answers, open this PDF file and look for section 1.7.