Re: Integrate product of Gaussian*Sin
- To: mathgroup at smc.vnet.net
- Subject: [mg6907] Re: [mg6855] Integrate product of Gaussian*Sin
- From: Richard Finley <trfin at fiona.umsmed.edu>
- Date: Fri, 25 Apr 1997 14:00:38 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
James, I am a little confused because there is an end bracket missing in your equation. I presume that you mean the integral: Integrate[Exp[-alpha*(x-a)^2]*Sin[n Pi x/L],{x,-Infinity,Infinity}] If this is the integral you are interested in there is no need to change variables because it is the integral of a product of odd and even functions over the real line and is therefore identically zero for all values of the parameters. hope that helps. regards, RF At 02:44 AM 4/24/97 -0400, you wrote: >Hi, > > Can anyone suggest a good change of variables to carry out the >integration > > Integrate[Exp[-alpha*(x-a)^2*Sin[n Pi x/L],{x,-Infinity,Infinity}] > > I can't find this form in my integral tables (I'm going to check >the library today for a more comprehensive list, I might find a form that I >can convert my expression to), and Mathematica can't find a solution unless >I take the limits of the integral {x,-c,c}. However, treated as an improper >integral > > Integrate[Exp[-alpha*(x-a)^2*Sin[n Pi x/L],{x,-c,c}] > Limit[%,c->Infinity] >or Limit[%,c->-Infinity] > > Still does not give a solution, since the answer to the integral >(with limits {x,-c,c}) is a combination of Erf[x] and Erfi[x], and the >Limit[Erfi[x],x->+/- Infinity]->+/- Infinity. The Erf[x] has a limit of +/- >1 as x->+/- Infinity. > I'm not sure if there is a solution to this, anyone with >Gaussian-type function experience? > >Thank you >Jim > > > >