Supplementary angles are a pair of angles that add up to 180 degrees. When two angles are supplementary, each angle is said to be the supplement of the other. For example, if one angle measures 120 degrees, its supplement would be an angle measuring 60 degrees, because 120 + 60 equals 180.

An angle is a measure of rotation or turning and is usually measured in degrees or radians. In geometry, an angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex. The size of an angle is determined by the amount of rotation from one ray to the other.

Supplementary angles are a pair of angles that add up to 180 degrees. When two angles are supplementary, each angle is said to be the supplement of the other.

A perpendicular angle is equal to a quarter of a full rotation. A perpendicular angle is measured as 90 degrees or 1/4 τ radians.