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MathGroup Archive 2002

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Re: confusion with triple integral...

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32484] Re: confusion with triple integral...
  • From: Harald Giese <Harald.Giese at gmxpro.de>
  • Date: Wed, 23 Jan 2002 01:00:01 -0500 (EST)
  • References: <a2j8o9$79j$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Bradley Stoll wrote:
> 
> Please consider the Integral[r^2Sin[x]drdxdy] with limits as follows:
> [0,2Pi]for y, [0,ArcCos[1/4]] for x and [0,1/Cos[x]] for r.  Mathematica returns
> 27Pi, which is correct.  But, if instead of using ArcCos[1/4], I use either
> ArcCos[0.25] or ArcCos[1/4]//N in the limits, Mathematica returns 43Pi.  Any idea
> why?j


Hi Bradley,

  Integrate[r^2*Sin[x], {x, 0, ArcCos[1/4]}, {y, 0, 2*Pi}, {r, 0,
1/Cos[x]}]

returns

  5*Pi 

on my Mathematica 4.1 (Windows);
with the limit {x, 0, ArcCos[0.25]} the result is 15.708

Regards
Harald

-- 
Harald Giese
Hamburg, Germany


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