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MathGroup Archive 2002

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Re: confusion with triple integral...

  • To: mathgroup at
  • Subject: [mg32485] Re: confusion with triple integral...
  • From: "Dave Snead" <dsnead6 at>
  • Date: Wed, 23 Jan 2002 01:00:03 -0500 (EST)
  • References: <a2j8o9$79j$>
  • Sender: owner-wri-mathgroup at

Bradley Stoll <BradleyS at> wrote in message
news:a2j8o9$79j$1 at
> 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
> 27Pi, which is correct.  But, if instead of using ArcCos[1/4], I use
> ArcCos[0.25] or ArcCos[1/4]//N in the limits, Mathematica returns 43Pi.
Any idea
> why?j
> Bradley Stoll
> San Jose, CA

I get a consistent 5 Pi for both these cases

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

5 \[Pi]

Integrate[r^2Sin[x],{y,0,2 Pi},{x,0,ArcCos[.25]},{r,0,1/Cos[x]}]


-- Dave Snead

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