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How to show the following summation is true?

  1. Mar 31, 2015 #1
    I need to prove that the following summation is true:

    ∑(-1)^n * cos(nx) / n^2 = (3x^2 - π^2)/12

    How would I tackle this problem?
  2. jcsd
  3. Apr 1, 2015 #2


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    Science Advisor

    Hint: [itex]\sum_{n=1}^{\infty}\frac{1}{n^{2}}=\frac{\pi^{2}}{6} [/itex]
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