You can put this solution on YOUR website! DeMoivre's Theorem is usually used to raise complex numbers to a power. So I suspect that you left out an exponent. If so and if you are still not able to figure out the problem after reading what follows, please repost your question.
(Note: For unknown reasons Algebra.com's formula software does not handle notation for inverse functions well. So I will use "acos" in place of cos^-1 and asin for sin^-1 in the expressions below.)
If all you have to do is rewrite the complex number in polar form then the formula is:
Using this on your complex number we get:
Simplifying:
Using degrees, . (Use for radians.) We now have:
With polar form and DeMoivre's Theorem, it is very easy to raise complex numbers to powers.