cos(7pi/4) + i sin(7pi/4)/ cos pi + i sin pi
now this im just stuck on
What are you trying to do? Simplify and express in Cartesian form? Then note:
$\displaystyle \cos \left( \frac{7 \pi}{4} \right) + i \sin \left( \frac{7 \pi}{4} \right) = \frac{1}{\sqrt{2}} - \frac{i}{\sqrt{2}}$.
$\displaystyle \cos \pi + i \sin \pi = -1$.
You must make it your business to learn the exact values of sin and cos of important special angles.