No need for Euler's formula.
You know that by the Binomial Theorem, and by DeMoivre's Theorem.
Try applying each of these to , setting them equal, and equating real and imaginary parts
thank you so much one more quick question, when solving square roots (or cube roots etc) of complex numbers, is there any specific patterns of what values of k to choose after equating the angles? I know for square roots the values of k taken are usually 0 and 1, but for cube roots some people take 0, 1, 2 and others take 0, 1, -1?