$\displaystyle \sum^ \infty_{n=1} \frac{1}{n}cosn\pi$ I know that the cosn(\pi) becomes (-1)^n, but what do I do with the (1/n) according nth term test?
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Originally Posted by saiyanmx89 $\displaystyle \sum^ \infty_{n=1} \frac{1}{n}cosn\pi$ I know that the cosn(\pi) becomes (-1)^n, but what do I do with the (1/n) according nth term test? Use the alternating series test: Alternating series test - Wikipedia, the free encyclopedia
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