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Re: Re: Mathematica Integration help

  • To: mathgroup at smc.vnet.net
  • Subject: [mg86178] Re: [mg86156] Re: Mathematica Integration help
  • From: Daniel Lichtblau <danl at wolfram.com>
  • Date: Wed, 5 Mar 2008 03:38:24 -0500 (EST)
  • References: <fqetdm$jjs$1@smc.vnet.net> <fqghfq$f5c$1@smc.vnet.net> <200803040707.CAA22493@smc.vnet.net>

Francogrex wrote:
> On Mar 3, 10:47 am, Jens-Peer Kuska <ku... at informatik.uni-leipzig.de>
> wrote:
> 
>>look what happens when you compute from:
>>res = Integrate[
>>   Product[1/(E^((Subscript[x, i] - \[Mu])^2/(2*\[Sigma]^2))*
>>       Sqrt[2*Pi*\[Sigma]^2]), {i, 1, n}], \[Mu]]
>>
>>D[res,\[Mu]]
>>
>>and see that the result is *not*
>>
>>Product[1/(E^((Subscript[x, i] - \[Mu])^2/(2*\[Sigma]^2))*
>>       Sqrt[2*Pi*\[Sigma]^2]), {i, 1, n}]
>>
>>this obvious a bug.
> 
> 
> The result is:
> 
> (1/(E^((\[Mu] - Subscript[x, i])^2/(2*\[Sigma]^2))*Sqrt[\[Sigma]^2]))^
>   n/(2*Pi)^(n/2)
> 
> Do you mean that it cannot reconstitute the product?
> 

He means that it is a bug. Specifically, the indefinite integral 
produced as 'res' is garbage.

This is the same bug that was reported to comp.soft-sys.math.mathematica 
by David Cantrell around 6 weeks ago:

http://forums.wolfram.com/mathgroup/archive/2008/Jan/msg00341.html

This has been fixed in the development kernel.

Daniel Lichtblau
Wolfram Research



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