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MathGroup Archive 1997

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Re: integration problem???

  • To: mathgroup at smc.vnet.net
  • Subject: [mg9282] Re: [mg9257] integration problem???
  • From: Allan Hayes <hay at haystack.demon.co.uk>
  • Date: Mon, 27 Oct 1997 02:46:53 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

"J. M. Reese" <eng484 at eng.abdn.ac.uk> [mg9257] integration problem???
writes

>I am trying to integrate the expression: ((2*r2-r1-r).^5).*(r.^(-8))
> with respect to r, between the limits r1=4.75e-4 to r2=2.25e-4.
>
> If I use Mathematica I get 1.9567e10 If I use quad8 in Matlab I get
> 1.156e07

Jason:
With Mathematica 3.0 on a NeXt and on a Mac I get answers consistent
with   the Matlab answer.

r1 =4.75 10^-4;r2=2.25 10^-4;

Integrate[((2*r2-r1-r)^5)*(r^(-8)),{r,r1,r2}]

	1.156406983991509*^7

NIntegrate[((2*r2-r1-r)^5)*(r^(-8)),{r,r1,r2}]

	1.15640698399151*^7

r1 =475 10^-6;r2=225 10^-6;

The exact answer is

Integrate[ ((2*r2-r1-r)^5)*(r^(-8)),{r,r1,r2}]

	346083997600000000000000/29927525723291637

Which gives
N[%]

	1.156406983991509*^7
	
Allan Hayes
hay at haystack.demon.co.uk
http://www.haystack.demon.co.uk/training.html voice:+44 (0)116 2714198
fax: +44 (0)116 2718642
Leicester,  UK



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