Hello, dashreeve!

We have: .Use DeMoivre's Theorem to find: .

I start by putting the complex number in trig form, but am having trouble with the angle.

I have: . . . . . Good!

. . And: . .[1]

. . Then: .

We can use DeMoivre's Theorem to derive the following identities:

. .

Hence: .

. . . . . . . . . . . . . .

Then substitute the values from [1].