# Math Help - Prove the following beautiful identity of the square root of 7.

1. ## Prove the following beautiful identity of the square root of 7.

Prove the identity

$-\sin \frac{\pi}{7} + \sin \frac{2\pi}{7} + \sin \frac{3\pi}{7} + \sin \frac{4\pi}{7}+\sin \frac{5\pi}{7} - \sin \frac{6\pi}{7} = \sqrt{7}$

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2. Still working on the identity (nice one!), but

Originally Posted by mathwizard
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