# Cosine of Complement equals Sine/Proof 2

$\map \cos {\dfrac \pi 2 - \theta} = \sin \theta$
 $\displaystyle \cos \left({\frac \pi 2 - \theta}\right)$ $=$ $\displaystyle \cos \left({\theta - \frac \pi 2}\right)$ Cosine Function is Even $\displaystyle$ $=$ $\displaystyle \sin \left({\theta - \frac \pi 2 + \frac \pi 2}\right)$ Sine of Angle plus Right Angle $\displaystyle$ $=$ $\displaystyle \sin \theta$
$\blacksquare$