Cofunction Identities for Sine and Cosine
Cofunction Identities for Sine and Cosine
The cofunction identities for sine and cosine state that the cosine of an angle equals the sine of its complement and the sine of an angle equals the cosine of its complement. The hypotenuse in the above figure is of unit length, so that the sine of an angle is the length of the opposite side, and the cosine of an angle is the length of the side adjacent to it.