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RE: How to Integrate[Abs[x]]?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91626] RE: [mg91624] How to Integrate[Abs[x]]?
  • From: "Jaccard Florian" <Florian.Jaccard at he-arc.ch>
  • Date: Sat, 30 Aug 2008 01:49:53 -0400 (EDT)
  • References: <200808290825.EAA24127@smc.vnet.net>

Hello,

It's because Mathematica considers x as a Complex number.
So you can do it like this :

In[35]:= Assuming[Element[x, Reals], Integrate[Abs[x], x]]

Out[35]= Piecewise[{{-(x^2/2), x <= 0}}, x^2/2]


Or like this :

In[36]:= Integrate[Sqrt[x^2], x]

Out[36]= (x*Sqrt[x^2])/2


Regards,

F.Jaccard

-----Message d'origine-----
De : Thomas Dybdahl Ahle [mailto:lobais at gmail.com]
Envoy=E9 : vendredi, 29. ao=FBt 2008 10:26
=C0 : mathgroup at smc.vnet.net
Objet : [mg91624] How to Integrate[Abs[x]]?

On my Ti calculater |x| is easily integrated to |x|*x/2, but when I type =
Integrate[Abs[x],x] in mathematica, it seams like it can't find the =
solution.
Is there anything I'll have to do, to make mathematica find the =
solution?



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