The question asks me to find the solution to $\displaystyle z^{3}=3^{\frac{1}{2}}+i$ in polar form.

I got

$\displaystyle 1^{\frac{1}{3}}cis(\frac{\pi}{18})$

Which is correct, but there 2 other answers but I can't seem to get it which are

$\displaystyle 1^{\frac{1}{3}}cis(\frac{13\pi}{18})$

And

$\displaystyle 1^{\frac{1}{3}}cis(\frac{-11\pi}{18})$

There's also another question I don't understand:

"How many degrees apart are two consecutive roots of $\displaystyle z^{8}=1$"