Sine of 22.5 Degrees

Theorem

 * $\sin 22.5 \degrees = \sin \dfrac \pi 8 = \dfrac 1 2 \sqrt {2 - \sqrt 2}$

where $\sin$ denotes sine.

Also see

 * Cosine of $22.5 \degrees$
 * Tangent of $22.5 \degrees$