Path: news.mathworks.com!newsfeed-00.mathworks.com!news.kjsl.com!usenet.stanford.edu!elk.ncren.net!newsflash.concordia.ca!canopus.cc.umanitoba.ca!not-for-mail From: Walter Roberson <roberson@hushmail.com> 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$1@canopus.cc.umanitoba.ca> References: <hph299$vn$1@fred.mathworks.com> NNTP-Posting-Host: ssh.ibd.nrc.ca Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: canopus.cc.umanitoba.ca 1270651780 28384 132.246.132.10 (7 Apr 2010 14:49:40 GMT) X-Complaints-To: abuse@cc.umanitoba.ca NNTP-Posting-Date: Wed, 7 Apr 2010 14:49:40 +0000 (UTC) User-Agent: Thunderbird 2.0.0.24 (Macintosh/20100228) In-Reply-To: <hph299$vn$1@fred.mathworks.com> Xref: news.mathworks.com 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.