Re: Integral giving complex answer
- To: mathgroup at smc.vnet.net
- Subject: [mg59302] Re: Integral giving complex answer
- From: Peter Breitfeld <phbrf at t-online.de>
- Date: Fri, 5 Aug 2005 01:21:29 -0400 (EDT)
- References: <200508030519.BAA06368@smc.vnet.net> <dcsc1v$pvn$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Pratik Desai schrieb:
> David Sagan wrote:
>
>>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
>>
>>
>>
> I works fine on my Ver 5.1.1.0 Win Xp
> Integrate[1/(1 + 5x^2), x]
> >>\!\(ArcTan[\@5\ x]\/\@5\)
>
I get the complex solution too with Mathematica 5.0 for Macintosh.
But you cat get the arctan solution using ComplexExpand with
TargetFunctions->{Re, Im}.
Gruss Peter
--
==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de
- References:
- Integral giving complex answer
- From: David Sagan <dcs16@cornell.dot.edu>
- Integral giving complex answer