# How can you use trigonometric functions to simplify  17 e^( ( 4 pi)/3 i )  into a non-exponential complex number?

$-$17/2 ( 1 + sqrt3 i)
r = 17, $\theta$ = $4 \frac{\pi}{3}$
x = r cos $\theta$ and y = r sin $\theta$.
Also, cos ( $\pi$ + $\theta$) = $- \cos \theta$ and sin ( $\pi$ + $\theta$) = $- \sin \theta$.