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(Newbie) More confusion with integral of absolute vals

  • To: mathgroup at smc.vnet.net
  • Subject: [mg9367] (Newbie) More confusion with integral of absolute vals
  • From: "L. Dwynn Lafleur" <lafleur at usl.edu>
  • Date: Sat, 1 Nov 1997 03:33:53 -0500
  • Organization: U. of Southwestern Louisiana
  • Sender: owner-wri-mathgroup at wolfram.com

Suppose I want to integrate the absolute value of x over the range a->b.
It's simple enough in Maple V Release 4:

> ii:=int(abs(x),x=a..b);

                         2                  2
              ii := 1/2 b  signum(b) - 1/2 a  signum(a)

> assume(0<a,a<b);
> ii;

                                2         2
                          1/2 b~  - 1/2 a~

where the tildes (~) indicate there are assumed properties for a and b.

If I try the same thing in Mathematica 3.01, I get 

In[1]:= ii=Integrate[Abs[x],{x,a,b}] Out[1]= $Aborted

In other words, Mathematica cannot perform the integral and I must abort
the evaluation.  Even if I try to place Assumptions in the Integrate
function, the integration is not performed.  What am I missing here? 
Can't the integration be performed as easily in Mathematica as it is in
Maple?

-- 

=========================================== L. Dwynn Lafleur
Professor of Physics
The University of Southwestern Louisiana Lafayette, Louisiana  (USA)
lafleur at usl.edu               
===========================================



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