Cosine of Complement equals Sine/Proof 2

Theorem

$\map \cos {\dfrac \pi 2 - \theta} = \sin \theta$


Proof

\(\ds \map \cos {\frac \pi 2 - \theta}\) \(=\) \(\ds \map \cos {\theta - \frac \pi 2}\) Cosine Function is Even
\(\ds \) \(=\) \(\ds \map \sin {\theta - \frac \pi 2 + \frac \pi 2}\) Sine of Angle plus Right Angle
\(\ds \) \(=\) \(\ds \sin \theta\)

$\blacksquare$

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