Convergence of a Series with Trig Functions

HypeBeast23
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Homework Statement



*The sum from n = 1 to infinity* (cos(n*pi))^2/n*pi where n is the variable.

Homework Equations



All forms of convergence tests (i.e. Ratio Test, Integral Test, Alternating Series test etc.)

The Attempt at a Solution



I am having trouble figuring out which route to take to tackle this question. Any help would be appreciated!
 
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Try writing out the first few terms of the series. You'll see it's not as complicated as you think.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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