Putting trig on the coordinate plane is called *analytic geometry*. The starting point on the coordinate plane in the *origin*, where the *x-axis* and *y-axis* meet . The rotation starts from the right side of the *x-axis* and opens counter-clockwise.

The *initial side* comes from the origin along the *x-axis* towards the right (positives). The *terminal side* is drawn **counter-clockwise** around the origin. The angle is between the initial side and the terminal side.

This is called **standard postion** of an angle.