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MathGroup Archive 2004

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Re: How to find out the transformation used in Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51462] Re: How to find out the transformation used in Mathematica
  • From: carlos at colorado.edu (Carlos Felippa)
  • Date: Sun, 17 Oct 2004 21:49:58 -0400 (EDT)
  • References: <ckt7jn$7cv$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Ann Lee <kan2 at rogers.com> wrote in message news:<ckt7jn$7cv$1 at smc.vnet.net>...
> Hi,
> 
> 	I tried the following indefinite integral
> 
> Integrate[Exp[-x^2/2]/(4 + x^2), {x, -Infinity, Infinity}]
> 
> 	Mathematica gave me 
> 
> Pi*e^2*Erfc[Sqrt[2]]
> 
> 	which is very nice.  However, I don't know how Mathematica got
> this answer and would like to find out what kind of transformation
> that it uses to get this answer.  Is there anyway for us to ask
> Mathematica to provide the transformation that it uses to arrive at
> this answer.  Or alternatively, can anyone tell me how to get the
> integral above?
> 
> 
> Best,
> 
> Ann


Storing tables is one way. That integral is 7.4.11 of Abramowitz and
Stegun (1964)

Some tables, e.g. Gradshteyn, now come in cdrom with the results
typeset-ready  for cut & paste in TeX.


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