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Re: Help!!!!!!

• To: mathgroup at smc.vnet.net
• Subject: [mg6964] Re: [mg6911] Help!!!!!!
• From: jpk at max.mpae.gwdg.de
• Date: Wed, 30 Apr 1997 22:25:27 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

> From eguevara at campus.maz.itesm.mx Fri Apr 25 21:43:53 1997
> Date: Fri, 25 Apr 1997 14:00:40 -0400 (EDT)
> From: Eusebio Guevara Villegas <eguevara at campus.maz.itesm.mx>
> To: mathgroup at smc.vnet.net
> Subject: [mg6911] Help!!!!!!
> 
> I integrated the following equation: (e^(x^2)) with mathematica, and it
> give me the following result: (Sqrt[Pi] Erfi[x])/2. My question is: What
> the Erfi means...... I consult the kernel help and it is about Gaussian
> Distribution, but I don't know what it is?
> 
> Thanks for your help.
> Sinceresly
> Gustavo Lozano Ibarra
> al540562 at campus.maz.itesm.mx
> 
Hi Gustavo,

consult one of the standard books on special functions like
Abramowitz/Stegun. You will find that one of the possible 
definitions of the Erfi-Function is

Erfi[x]=2*Integrate[Exp[x^2],x]/Sqrt[Pi]

or Erf[I*z]/I -- so here is the answer:

Erfi is a function that is defined by a infinite series (like Exp, Sin,..)
and/or just by the integral above. 

Hope that helps
Jens