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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 18:35:36 +0000 (UTC)
Organization: National Research Council Canada - Conseil national de rechereches Canada
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In article <fvd1im$oli$1@fred.mathworks.com>,
David Doria <daviddoria@gmail.com> wrote:
>right - but that is not very useful because if I'm unsure of
>the domain of the correct answer then I still don't know the
>answer! Surely there is a function that can do this properly??

You haven't defined what you mean by "properly". k = -1 *is*
a correct answer for the problem you asked Matlab to solve,
int(x,x=0..k)=1/2 . If k < 0 is not feasible for your overall
task then that infeasibility knowledge must come from your knowledge
of the task, not from your asking Matlab to filter out solutions
that it cannot know are wrong because you are unable to tell it what
"wrong" means.

If you know the valid range of k, then you can add it as an
assumption or you can add the knowledge to the solve() call.
For example in maple directly,

> solve({int(x,x=0..k)=1/2,k>0});
                                    {k = 1}

-- 
   "I was very young in those days, but I was also rather dim."
   -- Christopher Priest