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- Jan 26, 2012
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Show that \(\displaystyle \cos \left( \frac{\pi}{7} \right)-\cos \left( \frac{2\pi}{7} \right)+\cos \left( \frac{3\pi}{7} \right)=\frac{1}{2}\)
Bonus:
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Bonus:
Show that the general form of \(\displaystyle \sum_{i=1}^{n}\cos \left( \frac{(2i-1)\pi}{2n+1} \right)\) is always one-half.
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Remember to read the POTW submission guidelines to find out how to submit your answers!
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