Here is a useful image of the unit circle labeled with the “special angles” and the coordinates of the corresponding points on the unit circle:
(via http://etc.usf.edu/clipart/43200/43215/unit-circle7_43215.htm)
This image is useful since you can use it to find the sine and cosine of any of the given angles, using the definitions of sin t and cos t as the y- and x-coordinates, respectively, of the point on the unit circle corresponding to the angle t:
