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Re: Incorrect integral in Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91385] Re: Incorrect integral in Mathematica
  • From: "David Park" <djmpark at comcast.net>
  • Date: Tue, 19 Aug 2008 07:15:56 -0400 (EDT)
  • References: <g8b8t8$8pq$1@smc.vnet.net>

You might try using the Assumptions option in the Integrate expression. In 
6.0.3 (and probably in 5.0) this gives:

Integrate[
 Exp[-x^2/(2 w^2)] Exp[-(y - y0)^2/(2 z^2)], {x, -Infinity,
  Infinity}, {y, -Infinity, Infinity},
 Assumptions -> w > 0 \[And] z > 0]

2 \[Pi] w z

-- 
David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/


"Eran Mukamel" <emukamel at stanford.edu> wrote in message 
news:g8b8t8$8pq$1 at smc.vnet.net...
> Hi All,
>
> I'm getting a nonsensical answer of 0 for the following integral in 
> Mathematica 5.0 (Mac OSX):
>
> Integrate[Exp[-x^2/(2w^2)]Exp[-(y - y0)^2/(2z^2)],
>  {x, -Infinity, Infinity}, {y, -Infinity, Infinity}]
>
> The result should be (2 Pi w z).  Any ideas why this fails?
>
> Thanks in advance, Eran
> 



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