## Introductory Algebra for College Students (7th Edition)

Complementary angles are two angles, when added together, equal 90°. To find an angle's complement, you subtract the measure of the known angle from 90°. In other words, the measure of an angle's complement can be found using the following formula, with $C$ as the measure of the complementary angle and $x$ is the measure of the known angle: $$C = 90° - x$$