From: Walter Roberson <>
Newsgroups: comp.soft-sys.matlab
Subject: Re: arc length
Date: Wed, 07 Apr 2010 09:49:39 -0500
Organization: The University of Manitoba
Lines: 12
Message-ID: <hpi624$rn0$>
References: <hph299$vn$>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Trace: 1270651780 28384 (7 Apr 2010 14:49:40 GMT)
NNTP-Posting-Date: Wed, 7 Apr 2010 14:49:40 +0000 (UTC)
User-Agent: Thunderbird (Macintosh/20100228)
In-Reply-To: <hph299$vn$>
Xref: comp.soft-sys.matlab:624270

bo wrote:

> How to calculate arc length between 2 different radius?As I only know, 
> the arc length inside circle is r*(theta2-theta1).

In addition to what Roger wrote: note that the integration that he 
suggests is correct in theory, but has the technical problem that closed 
forms for the calculation of arc length are known for only a relatively 
small number of shapes. For example there is a whole branch of calculus 
dealing with integration along ellipses, which there is no closed 
formula for, even though we think of them as being such a minor 
variation of circles.