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Integral giving complex answer

  • To: mathgroup at smc.vnet.net
  • Subject: [mg59251] Integral giving complex answer
  • From: David Sagan <dcs16 at cornell.dot.edu>
  • Date: Wed, 3 Aug 2005 01:19:54 -0400 (EDT)
  • Organization: Cornell University
  • Sender: owner-wri-mathgroup at wolfram.com

Hello:

I am tring to do simple integrals but I am running into problems in that 
Mathematica gives the answer using complex numbers. For example, 
Integrate[1/(1 + 5x^2), x] gives a result in terms of logarithms of a 
complex argument instead of the usual arctan formula. If I integrate 
something like Integrate[1/(1 + a x^2), x] I get the answer in the form 
I want using the arctan.

My question is how to avoid getting the answer to Integrate[1/(1 + 
5x^2), x] in terms of complex logarithms. I know I could just integrate 
1/(1 + a x^2) and substitute a -> 5 later but in actuality I am dealing 
with more complex integrals and it would be helpful if I did not have to 
be making such substitutions.

            -- Thanks for any help, David Sagan


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