Find the sine and cosine of π/4
The unit circle helps us to memorize common angle values. For $ \frac{\pi}{4} $, the coordinates are the same for both sine and cosine.
$$ \sin\left( \frac{\pi}{4} \right) = \frac{\sqrt{2}}{2} $$
$$ \cos\left( \frac{\pi}{4} \right) = \frac{\sqrt{2}}{2} $$