Re: Integration Problem

• To: mathgroup at smc.vnet.net
• Subject: [mg102141] Re: Integration Problem
• From: Pianiel <pdpdel at gmail.com>
• Date: Thu, 30 Jul 2009 05:34:38 -0400 (EDT)
• References: <h4h1vg\$ibr\$1@smc.vnet.net>

```On 26 juil, 09:52, JerrySpock <liquidsol... 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 i=
deas what I'm doing wrong?
>
>     [Edited by: admin on Jul 25, 2009 7:22 AM]

Hi,

I just sent a bug report to Wolfram with

Integrate[Sqrt[2 E^(3. m) + 4 E^m], {m, 1, 2}]
NIntegrate[Sqrt[2 E^(3. m) + 4 E^m], {m, 1, 2}]

shows the same strange behavior as your example.

Sincerely

Pianiel

```

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