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MathGroup Archive 2002

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Integrate malfunction?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg33860] Integrate malfunction?
  • From: "Steve Story" <sbstory at unity.ncsu.edu>
  • Date: Sat, 20 Apr 2002 02:49:51 -0400 (EDT)
  • Organization: NC State University
  • Sender: owner-wri-mathgroup at wolfram.com

I recently had to do an integral which should evaluate to be a very very
small quantity. The function is always positive, but the integral gives me a
negative number. I think this is a malfunction of some sort. Here's the
code:

amu = 1.661*10^-27
nitrogen = 28*amu
k = 1.381*10^-23
t = 1000

Integrate[
  4 Pi ((nitrogen/(2 Pi k t))^(3/2)) x^2 Exp[(-1 nitrogen x^2)/(2 k t)], {x,
11000, Infinity}]

Out[13]= -5.878291776559734*10^-16

does anyone know why this is happening? i tried NIntegrate instead, but it
said:

General::"unfl": "Underflow occurred in computation."

thanks,
Steve Story


_______________

Steve Story
Polymer NEXAFS Research Group
411B Cox
North Carolina State University
1-919-515-8147
sbstory at unity.ncsu.edu
_______________




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