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MathGroup Archive 2005

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Re: Integral problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58317] Re: Integral problem
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Tue, 28 Jun 2005 05:13:16 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, England
  • References: <d9num6$cl5$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

HUAFANG CUI wrote:
> Hi,
> 
> I have a question about integral.  I could not figure out what is wrong.
> 
> function is
> 0.5 * (1 + 10^7 * ((1-x-y)/1.5 + x/8)^10) + 0.004 * x / ((1-x-y)/1.5 + 
> x/8)^10)
> 
> limit on y is
> 0.8425 - x, 0.8
> 
> limit on x is
> 0.0425, 0.1999
> 
> I run it on Ver4.0.  It runs forever and does not stop.
> 
> Thank you.
> 
> HC
> 
Hi HC,

Assuming that I have made no mistake in copying your function, although 
it does not take forever to integrate it, Mathematica consumes a good 
deal of CPU time before displaying the result:

In[1]:=
Timing[Integrate[
    0.5*(1 + 10^7*((1 - x - y)/1.5 + x/8)^10) +
     0.004*(x/((1 - x - y)/1.5 + x/8)^10),
    {x, 0.0425, 0.1999}, {y, 0.8425 - x, 0.8}]]

Out[1]=
{379.906*Second, 1.91538522742034*^8}

(Tested on a Pentium IV 2.6GHz 512Mo Physical Ram, Windows XP SP2,
Mathematica 5.1.)

Best regards,
/J.M.

P.S. You should use the _InputForm_ when copying an expression from a 
Mathematica notebook to an email client: select the cell(s) you want to 
include in your email, then within the *Cell* menu select either 
*Convert To* or *Display As* and choose *InputForm*. Finally, copy and 
paste as usual.


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