RE: Re: PDE

*To*: mathgroup at smc.vnet.net*Subject*: [mg35328] RE: [mg35297] Re: PDE*From*: "DrBob" <majort at cox-internet.com>*Date*: Mon, 8 Jul 2002 03:19:56 -0400 (EDT)*Reply-to*: <drbob at bigfoot.com>*Sender*: owner-wri-mathgroup at wolfram.com

The sign of your eigenvalues is wrong: f = Sin[k x]*Sin[m y]; D[f, x, x] + D[f, y, y] // Factor (-(k^2 + m^2))*Sin[k*x]*Sin[m*y] Bobby -----Original Message----- From: Jens-Peer Kuska [mailto:kuska at informatik.uni-leipzig.de] To: mathgroup at smc.vnet.net Subject: [mg35328] [mg35297] Re: PDE Hi, no but ist is easy by hand -- use the eigenfunctions Sin[k Pi x/L]*Sin[m Pi y/L] and the eigenvalues k^2 Pi^2/L^2 + m^2 Pi^2/L^2 and use the Fourier series. That's the simplest example in standard text books about PDE's. You don't need a computer algebra for that. Regards Jens mitja Lakner wrote: > > Is there any package for solving eigenvalue problem for the Laplacian operator > on the 2D (not rectangular) region with zero boundary value? > > f_{xx}+f_{yy}= t f > > Mitja Lakner