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Indefinite Integral for -.5*(ln(2))^2

  1. Jul 24, 2012 #1
    Hello, I have recently encountered an integral that I have been able to evaluate in a sick, unholy way, and for making a proof much more elegant I would like a simple way to evaluate the integral from 0 to infinity of ln(x)/(e^x+1) . thank you!
  2. jcsd
  3. Jul 25, 2012 #2
    I haven't tried them but maybe differentiation under the integral sign (set 1 to any arbitrary number) and contour integration?
  4. Jul 25, 2012 #3
    Is the denominator you have listed e^(x+1) or (e^x)+1? Just want to verify before trying the problem.
  5. Jul 25, 2012 #4
    It is (e^x)+1 . I tried using limits on the bounds and then integration by parts and then switching certain values to other limited integrals and canceling... I tell you what that didn't work. I also tried a limit for the natural logarithm with an integral for the Dirichlet eta function, but that gave me a very tough looking limit that I had no chance with.

    edit: The limit was lim x->+1 ([itex]\Gamma[/itex](x)[itex]\eta[/itex](x)-ln(2))/(x-1) , if anyone has some cool trick for that.
    Last edited: Jul 25, 2012
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