I have difficulty doing this question, if anyone could help that would be greatly appreciated. Thx in advance
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$\displaystyle e^{3i \theta} = (e^{i \theta})^3 = (\cos \theta + i \sin \theta)^3$ so $\displaystyle \cos(3 \theta) + i \sin(3 \theta) = (\cos \theta + i \sin \theta)^3$. Expand the right hand side and equate real and imaginary parts.
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