# Cofunction Identities for Sine and Cosine

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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.

Contributed by: Chris Boucher (March 2011)

Open content licensed under CC BY-NC-SA

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"Cofunction Identities for Sine and Cosine"

http://demonstrations.wolfram.com/CofunctionIdentitiesForSineAndCosine/

Wolfram Demonstrations Project

Published: March 7 2011