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Math Help - another ratio test

  1. #1
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    another ratio test

    \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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  2. #2
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    Quote Originally Posted by saiyanmx89 View Post
    \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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