# How do you find the exact values sin (pi/4) using the special triangles?

$\sin \left(\frac{\pi}{4}\right) = \frac{1}{\sqrt{2}} = \frac{\sqrt{2}}{2}$
$\frac{\pi}{4}$ is one of the "special triangle" angles:
$\textcolor{w h i t e}{\text{XXXX}}$$\sin = \left(\text{opposite")/("hypotenuse}\right)$