What is a terminal side?

In mathematics, a terminal side is the side of an angle that rotates counterclockwise from the initial side to the position of the angle in standard position. It is the final position of the angle after it has been rotated from its initial position.

The terminal side of an angle is used to determine the measure of the angle in both degrees and radians. The angle is measured in standard position, where the vertex of the angle is at the origin of a coordinate plane, and the initial side is on the positive x-axis.

The terminal side is important in trigonometry, as it helps determine the direction of the angle and the trigonometric functions associated with that angle. It is also used to find the reference angle, which is the acute angle formed between the terminal side and the x-axis.

In summary, the terminal side of an angle is the side of the angle that extends from the origin of a coordinate plane to the position of the angle in standard position after rotating counterclockwise from the initial side. It is used to determine the measure of the angle and its trigonometric functions.