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**WWTL@WHL** Hey guys, I'm totally stumped on this question. Any help will be appreciated.

__Question:__

For a real number $\displaystyle \theta$, define

$\displaystyle e^{i \theta} = \cos \theta + i \sin \theta $

Show that the identity $\displaystyle e^{i(\theta + k)} = e^{i \theta}e^{i k} $ is equivalent to the trigonometric rules:

$\displaystyle \cos (\theta + k) = \cos \theta \cos k - \sin \theta \sin k $

$\displaystyle \sin (\theta + k) = \sin \theta \cos k + \cos \theta \sin k $