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Re: Integration Problem

  • To: mathgroup at
  • Subject: [mg102022] Re: [mg102004] Integration Problem
  • From: Bob Hanlon <hanlonr at>
  • Date: Mon, 27 Jul 2009 05:52:57 -0400 (EDT)
  • Reply-to: hanlonr at

The problem arises with the use of inexact numbers in the exponent while trying to do exact integration

Integrate[Sqrt[(2 Exp[2*m])^2 + (1.5 Exp[1.5*m])^2], {m, 1, 2}]


Using purely numerical

NIntegrate[Sqrt[(2 Exp[2*m])^2 + (1.5 Exp[1.5*m])^2], {m, 1, 2}]


Or using exact exponents

N[Integrate[Sqrt[(2 Exp[2*m])^2 + (3/2 Exp[3/2*m])^2], {m, 1, 2}]]


Bob Hanlon

---- JerrySpock <liquidsolids at> wrote: 

Hello, everyone.

I'm having a problem integrating to find an arc length.

I have two parametric equations:




I'm looking for the arc length from 1 to 2.

(2Exp[2*m])^2 + (1.5Exp[1.5*m])^2
],{m, 1, 2}]]

I keep getting the answer 79.6, but my TI-83 says the answer is 49.8.  I've been playing with this for hours, and I can't get it to work.  Any ideas what I'm doing wrong?

    [Edited by: admin on Jul 25, 2009 7:22 AM]

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