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Thread: Sum of squares of cosine.

  1. February 26th 2011, 10:25 AM #1
    arm
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    Sum of squares of cosine.

    Find: cos ^{2}(\frac{\pi }{5})+ cos^{2} (\frac{2\pi }{15})+ cos^{2} (\frac{8\pi }{15})
    Last edited by mr fantastic; February 26th 2011 at 12:56 PM. Reason: Re-titled.
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  2. February 26th 2011, 12:56 PM #2
    mr fantastic
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    Quote Originally Posted by arm View Post
    Find: cos ^{2}(\frac{\pi }{5})+ cos^{2} (\frac{2\pi }{15})+ cos^{2} (\frac{8\pi }{15})
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