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MathGroup Archive 1997

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Re: False result with Integrate ?

  • To: mathgroup at
  • Subject: [mg8729] Re: False result with Integrate ?
  • From: "Stephen P Luttrell" <luttrell at>
  • Date: Sat, 20 Sep 1997 22:27:58 -0400
  • Organization: Defence Evaluation and Research Agency
  • Sender: owner-wri-mathgroup at

Gilles BARBIER <Gilles.Barbier at> wrote in article
<5vt8tj$gjg at>...
>      Why : Integrate[Integrate[ Sqrt[(x-y)^2],{x,0,1}],{y,0,1}]
>      gives 0 with math2.2 or math3.0.
>      The exact result is 1/3 !!

It seems that Mathematica is simplifying Sqrt[(x-y)^2] to x-y.

Try the following way of doing your integral:

2 Integrate[Integrate[ x-y,{x,y,1}],{y,0,1}]

Stephen P Luttrell                                      
luttrell at
Adaptive Systems Theory                           01684-894046 (phone)
Room EX21, DERA                                    01684-894384 (fax)      
Malvern, Worcs, WR14 3PS, U.K.   

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