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Strange results of Integrate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92874] Strange results of Integrate
  • From: osepsi <sepsi.ors at gmail.com>
  • Date: Thu, 16 Oct 2008 05:05:55 -0400 (EDT)

Dear Group,

I wanted to solve the following integral:

Integrate[Exp[I*k*Sqrt[x^2+y^2+z^2]]/Sqrt[x^2+y^2+z^2],{x,-a,a},{y,-
b,b},{z,-c,c}]

The result was 0. (It is wrong solution...)

Replacing b and c with a gives back the integral unevaluated.
With NIntegrate I have the result, but with some warning messages.

Questions:
1. Why gives Mathematica the wrong answer for the first formula?
2. Does anyone know the right method (Method->...) for numerical
integration of this type of integral.

Thanks, =D6rs


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