Re: Integration Problem
- To: mathgroup at smc.vnet.net
- Subject: [mg102022] Re: [mg102004] Integration Problem
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Mon, 27 Jul 2009 05:52:57 -0400 (EDT)
- Reply-to: hanlonr at cox.net
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}]
79.6261
Using purely numerical
NIntegrate[Sqrt[(2 Exp[2*m])^2 + (1.5 Exp[1.5*m])^2], {m, 1, 2}]
49.7621
Or using exact exponents
N[Integrate[Sqrt[(2 Exp[2*m])^2 + (3/2 Exp[3/2*m])^2], {m, 1, 2}]]
49.7621
Bob Hanlon
---- JerrySpock <liquidsolids at hotmail.com> wrote:
=============
Hello, everyone.
I'm having a problem integrating to find an arc length.
I have two parametric equations:
x=e^(2t)
and
y=e^(1.5t)
I'm looking for the arc length from 1 to 2.
N[
Integrate[
Sqrt[
(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]