# Math Help - Question regarding polar form of complex numbers

1. ## Question regarding polar form of complex numbers

I have difficulty doing this question, if anyone could help that would be greatly appreciated.

Thx in advance

2. $e^{3i \theta} = (e^{i \theta})^3 = (\cos \theta + i \sin \theta)^3$

so

$\cos(3 \theta) + i \sin(3 \theta) = (\cos \theta + i \sin \theta)^3$.

Expand the right hand side and equate real and imaginary parts.