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MathGroup Archive 2004

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Re: Simple question or how Mathematica getting on my nerves.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg45788] Re: Simple question or how Mathematica getting on my nerves.
  • From: bobhanlon at aol.com (Bob Hanlon)
  • Date: Sun, 25 Jan 2004 03:04:43 -0500 (EST)
  • References: <butdvt$9se$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

$Version

5.0 for Mac OS X (November 19, 2003)

They aren't the same because you had the computations done at diifferent
precisions.  Different result indicates that there is a precision problem. 
Solution is to use higher precision.

k[f_] := 2687176093959399272413585923303421161600*
   (1 - f)^67*f^61

N[Integrate[k[f], {f, 6214/10000, 5242/10000}]]

-0.139838

N[Integrate[k[f], {f, 0.6214`45, 0.5242`45}]]

-0.139838

Although NIntegrate works without explicitly increasing the precision.  So the
precision is impacted by the sequencing of the calculations.

NIntegrate[k[f], {f, 0.6214, 0.5242}]

-0.139838


Bob Hanlon

In article <butdvt$9se$1 at smc.vnet.net>, gtsavdar at auth.gr (George) wrote:

<< Although the 2 results must be the same they aren't. WHY???????
And not only this, but they differ by 10^21!!!!!! WHY???????? 

Please copy and paste this to Mathematica (i tried 5.0 and 4.2) to
understand what i mean:


\!\(k[f_] := 
    2687176093959399272413585923303421161600\ *\((1 - f)\)\^67\ *
      f\^61\[IndentingNewLine]
  N[\[Integral]\_\(6214\/10000\)\%\(5242\/10000\)k[
          f] \[DifferentialD]f]\[IndentingNewLine]
  N[\[Integral]\_0.6214\%0.5242 k[f] \[DifferentialD]f]\)


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