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Re: A problem with an integral


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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