Question

use Demoivre's theorem to find the power [5(cos3.2 + isin3.2)]^4

Answer 1

Is the 3.2 in radians?

First, factor out 5^4 = 625.

Then review and apply De Moivre's theorem. For any x,
(cosx + i sinx)^n = cos(nx) + i sin(nx)