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