Measuring Rotation
Key Questions

Negative angles has to do with the direction of rotation that you consider in order to measure angles.
Normally you start counting your angles from the positive side of the x axis in an anticlockwise direction of rotation:
You can also go clockwise and so to avoid confusion you use a negative sign to indicate this kind of rotation.

You can draw an angle in standard position by positioning its vertex at the origin and one "ray" on the positive xaxis. The ray on the xaxis is called the initial side and the other ray is called the terminal side.
An angle is then measured POSITIVE for a counterclockwise rotation and NEGATIVE for a clockwise rotation:
When two angles have the same initial and terminal sides, they are said to be coterminal angles.
Angles of −315° and 45° are coterminal angles.

Answer:
As discussed below.
Explanation:
Coterminal Angles are angles who share the same initial side and terminal sides. Finding coterminal angles is as simple as adding or subtracting 360° or 2π to each angle, depending on whether the given angle is in degrees or radians.
For example, the angles 30°, –330° and 390° are all coterminal.
What is the terminal side?
Standard Position of an Angle  Initial Side  Terminal Side. An angle is in standard position in the coordinate plane if its vertex is located at the origin and one ray is on the positive xaxis. The ray on the xaxis is called the initial side and the other ray is called the terminal side.