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Re: help with integration

  • To: mathgroup at smc.vnet.net
  • Subject: [mg121659] Re: help with integration
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Sat, 24 Sep 2011 22:33:29 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

On 9/23/11 at 3:43 AM, dsalman96 at yahoo.com (Salman Durrani) wrote:

>I am trying to do the following integration:

>Integrate[r^2*ArcCos[x/r] - x*Sqrt[r^2 - x^2], {x, Sqrt[3] y,
>Sqrt[r^2 - y^2]} ]

>When I try, Mathematica comes back to be with a very long
>conditional expression.

>How do I tell mathematica that r is positive, real in the above
>equation not complex.

Use Assuming to specify your assumptions. Doing

Assuming[r>0, Integrate[...]]

is sufficient to specify r is real and positive. However, to
eliminate the conditional expression for this particular
integral you will need

Assuming[r>2Y&&y>0,Integrate[...]]





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