Some Basic Identities

idcirc2.eps

Using the coordinates a and b for a given point on the unit circle, we can find the coordinates of some related points in the above figure. Since and , we easily get the sine and cosine of other angles, such as , , , , and . You should be able to verify the following identities.

1. .
2. .
3. .
4. .
5. .
6. .
7. .
8. .
9. .
10. .