Question

prove that
$\cos( \frac{\pi}{4} + x ) + \cos( \frac{\pi}{4} - x ) = \sqrt{2 \cos(x) }$
prove that
$\cos( \frac{\pi}{4} + x) + \cos( \frac{\pi}{4} + x ) = \sqrt{2 \: \cos(x) }$
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Answer 1

Answer:

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