Re: Integrate returns 0
- To: mathgroup at smc.vnet.net
- Subject: [mg23916] Re: Integrate returns 0
- From: "Kevin J. McCann" <Kevin.McCann at jhuapl.edu>
- Date: Fri, 16 Jun 2000 00:56:56 -0400 (EDT)
- Organization: Johns Hopkins University Applied Physics Lab, Laurel, MD, USA
- References: <8i9pj8$2hq@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Probably not a bug, but how Mathematica treats the derivative. I suspect that Mathematica does not evaluate the derivative within the integral. It would require that Mathematica first find a general closed-form expression for the derivative, and then evaluate that. BTW, the general answer is (2n)!/(2^n n!)*Sqrt[Pi/2] for integer n. Looks like it has something to do with Legendre polynomials. Kevin Felix E. Klee <felix.klee at inka.de> wrote in message news:8i9pj8$2hq at smc.vnet.net... > Hi, > > when I define the function > f[x_,n_]:=D[Exp[-x^2],{x,n}]^2 > and execute > Integrate[f[x,n],{x,-Infinity,Infinity}] > the result is > 0 > > However this is not correct for all parameters n since > Integrate[f[x,1],{x,-Infinity,Infinity}] > returns > Sqrt[Pi/2] > > Is this a bug in Mathematica or am I doing something wrong? > > TIA, > > Felix >