# How do you evaluate sin ((7pi)/4)?

$- \frac{\sqrt{2}}{2}$
$\sin \left(\frac{7 \pi}{4}\right) = \sin \left(- \frac{\pi}{4} + \frac{8 \pi}{4}\right) = \sin \left(- \frac{\pi}{4} + 2 \pi\right) =$
$= \sin \left(- \frac{\pi}{4}\right) = - \sin \left(\frac{\pi}{4}\right) = - \frac{\sqrt{2}}{2}$