How do I evaluate $\cos(x) + \cos (2x) +\cos (3x) + ... + \cos (nx)$?
1,215
hint multiply numerator and denominator by $\sin(x/2)$ and then use a telescopic series.
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Updated on September 13, 2022Comments
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Admin about 1 year
How to evaluate the above expression and express the answer in terms of $n$ and $x$?