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MathGroup Archive 1998

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A couple of curious outputs from Integrate[]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg13626] A couple of curious outputs from Integrate[]
  • From: lawry at maths.ox.ac.uk (James Lawry)
  • Date: Fri, 7 Aug 1998 03:08:27 -0400
  • Organization: Oxford Centre for Industrial & Applied Mathematics
  • Sender: owner-wri-mathgroup at wolfram.com

Here are a couple of Integrate[] commands that produce very odd results
in Mathematica 3.0 for Sparc.

1: Try
Integrate[Exp[-x Log[x]] Sin[x], {x, 0, Infinity}]

This returns a value that contains x. This is silly, since it is a
definite integral and x is a dummy variable of integration. Version 2.2
returned this integral unevaluated.

2: Make sure that there's nothing unsaved in your Mathematica session,
and try

Integrate[Log[x]^2 Exp[-x], {x, 0, Infinity}]

This produces more spectacular results in the Sparc notebook version of
Mathematica than in the text version, which just grumbles loudly for
several minutes before producing the answer. Version 2.2 of Mathematica
produced the answer in a few seconds.

James Lawry.



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