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MathGroup Archive 2011

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get rid of I in the result of an integral

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116496] get rid of I in the result of an integral
  • From: Ruth Lazkoz Sáez <ruth.lazkoz at ehu.es>
  • Date: Thu, 17 Feb 2011 05:18:09 -0500 (EST)

Hi,

When I do Integrate[1/((1 + y)^2 Sqrt[-x^2 + y^2]), {y, x, Infinity},
  Assumptions -> x^2 < 1 && 1 > x > 0 && Element[x, Reals]]

I get

(-1 + x^2 - I Sqrt[1 - x^2] ArcSec[x])/(-1 + x^2)^2

and I would like the result expresed in terms of ArcSech[x] so that I 
does not appear.

I know I can tell Mathematica to do the replacement afterwards, but I 
want to show the result to a colleague who is not so familiar with 
mathematica, and if it were possible to get the result in one go just by 
adding some extra assumption or so, it would be more convincing.

Help will be appreciated. Best,

Ruth




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