Sine of Complement equals Cosine

Theorem

 * $\sin \left({\dfrac \pi 2 - \theta}\right) = \cos \theta$

where $\sin$ and $\cos$ are sine and cosine respectively.

That is, the cosine of an angle is the sine of its complement.

Also see

 * Cosine of Complement equals Sine
 * Tangent of Complement equals Cotangent
 * Cotangent of Complement equals Tangent
 * Secant of Complement equals Cosecant
 * Cosecant of Complement equals Secant