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From: roberson@ibd.nrc-cnrc.gc.ca (Walter Roberson)
Newsgroups: comp.soft-sys.matlab
Subject: Re: solve equations for integral limits?
Date: Thu, 1 May 2008 18:12:39 +0000 (UTC)
Organization: National Research Council Canada - Conseil national de rechereches Canada
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In article <fvcvu6$ld4$1@fred.mathworks.com>,
David Doria <daviddoria@gmail.com> wrote:
>so realizing that solve() uses maple... I used maple syntax:

>solve('int(x,x=0..k)=1/2','k')

>and it kind of works... the problem is that it returns [1,
>-1].  1 is clearly the correct solution, and -1 seems to be
>wrong... because if you integrate from 0 to -1, you have to
>switch the limits and change the sign... so you actually get
>-1/2, not 1/2 as requested...

int(x,x=a..b) is b^2/2-a^2/2
so int(x,x=-1..0) is 0^2/2-(-1)^2/2 = -1/2
so int(x,x=0..-1) is the negative of that, and -(-1/2) is 1/2.
Thus k=-1 is a correct solution to the problem.
-- 
   "No one has the right to destroy another person's belief by
   demanding empirical evidence."                -- Ann Landers