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MathGroup Archive 2002

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Re: A problem with an integral

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32806] Re: A problem with an integral
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Thu, 14 Feb 2002 01:43:20 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <a4aurc$buv$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hi, 

no you code is right but Mathematica take a  different
path to compute

Integrate[Sin[x y], {y, 0, x}]

with it's singularity at x==0

Regards
  Jens

WhoamI wrote:
> 
> Hi everybody, I have a problem with the next integral
> 
>   Integrate[Sin[x y],{x,0,1},{y,0,x}]
> 
> that after expanding and factoring yields:
> 
> \!\(1\/4\ \((EulerGamma - 2\ CosIntegral[1])\)\)
> 
>    and evaluating this I have -0.024398
> 
> To be sure about the answer I taked it other way:
> 
> Integrate[
>     TrigFactor[Integrate[Sin[x y], {y, 0, x}]]
>     , {x, 0, 1}]
> 
> which yields
> 
> \!\(1\/2\ \((EulerGamma - CosIntegral[1])\)\)
> 
> and evaluating this I have 0.119906
> 
> Since I evaluated this integrals not numerically I
> don't understand why the answers are different. Is
> there something wrong with my code?. I would thanks a
> lot for your answers...
> 
> Cesar Guerra
> Secc. Fisica PUCP-Lima
> 
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