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MathGroup Archive 2001

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NIntegrate with floating point limits

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28864] NIntegrate with floating point limits
  • From: "Fred Simons" <f.h.simons at tue.nl>
  • Date: Wed, 16 May 2001 03:28:11 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear mathgroup,

Can someone explain why the following integral can only be computed
numerically with exact limits and not with a floating point limit?

x = 1/4; NIntegrate[ CosIntegral[(x - u)/x + 1] - CosIntegral[1 - (x -
u)/x], {u, 0, x}]

returns 0.2362;

x = N[1/4]; NIntegrate[ CosIntegral[(x - u)/x + 1] - CosIntegral[1 - (x -
u)/x], {u, 0, x}]

returns some complaints and no result.

In all cases I met so far, floating points limits in numerical integration
caused no problems.

Many thanks in advance,

Fred Simons




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