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Topic: little brain teaser
Replies: 2   Last Post: Sep 16, 1996 2:39 PM

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Dr. H.M.A. Winand

Posts: 5
Registered: 12/11/04
Re: little brain teaser
Posted: Sep 16, 1996 2:39 PM
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On Fri, 13 Sep 1996, Jerry Clark wrote:

> Dr. H.M.A. Winand wrote:
> >
> > Dear All,
> >
> > Any idea on how to solve this little brain teaser without having a
> > series-type solution?
> >
> > Integrate[Exp[(-a^2 x^2)/2] Erf[k x], {x,y,Infinity}]
> >
> > where a and k are real, y takes values from -Infinity to +Infinity, but is
> > generally within +/-3.
> >
> > Any help would be greatly appreciated, and replies can also be e-mailed
> > to: Prof. D. J. Whitehouse, djw@eng.warwick.ac.uk or to my address.
> >
> > Best regards,
> >
> > Dr. Henri M.A. Winand
> >
> > P.S. If you wish to propagate this to other math-type newsgroups, etc.,
> > feel free to do so...both the hand-and-paper and Mathematica solutions
> > will not give us what we want (i.e. an exact sol. without series).

>
> er.. what's Erf? Is it something Cockneys spread on their gardens?
> Please explain.
>
> --JC
>
>


Jerry,

Well, Erf[x] stands for 'error function'. That is to say, the integral of
the Gaussian distribution given by:

Erf[x] := (2/SQRT[Pi]) * Integrate[Exp[-t^2],{t,0,z}].

I hope this helps,

Henri










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