Posts Tagged ‘Telescoping Series’

Monday Math 158

August 11, 2014

Find a non-summation expression for the value of the sum \cos{x}+2\cos{2x}+3\cos{3x}+\cdots+n\cos{nx}.

Solution:

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Monday Math 139

October 18, 2010

Prove that for positive integers k, m, and n, that
\sin\frac{k\pi}n\sin\frac{m\pi}n=\left(\sin\frac{\pi}n\right)\sum_{i=1}^{m}\sin\frac{(k-m+2i-1)\pi}n.
Solution: