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

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

    Quote Originally Posted by mathwizard View Post
    P.S. If I find a question interesting, is there a way to save the thread to look at it later (ex. using "favorite" or "private watch list"). Is there such facility in this forum? I couldn't find any means of saving a question that I like...
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