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MathGroup Archive 2002

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A problem with an integral

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32801] A problem with an integral
  • From: WhoamI <lushstring at yahoo.com>
  • Date: Tue, 12 Feb 2002 06:23:59 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

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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