This picture shows an animation of the sine function and its relation to the unit circle. The function y=sin(t) is related to the unit circle in the following manner: The angle t (blue angle measure) is the t coordinate in the ordered pair (t, sin(t)). The value of the sine is the displacement of the red dot from the t-axis. The function is 2 π periodic.

This picture shows an animation of the cosine function and its relation to the unit circle. The function y=cos(t) is related to the unit circle in the following manner: The angle t (blue angle measure) is the t coordinate in the ordered pair (t, cos(t)). The value of the cosine is the displacement of the red dot from the y-axis. The function is 2 π periodic.