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MathGroup Archive 2006

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Re: Re: Simplifying in Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71247] Re: [mg71200] Re: Simplifying in Mathematica
  • From: Daniel Lichtblau <danl at wolfram.com>
  • Date: Sat, 11 Nov 2006 03:39:27 -0500 (EST)
  • References: <eish5b$nq1$1@smc.vnet.net> <200611101138.GAA13711@smc.vnet.net>

pierodancona at gmail.com wrote:
> Define a function (depending on the variables B,b,A,a,c,d...etc,
> all of them) equal to your expression, and compute it at many points.
> If the expression is 0, the result should always be 0. Notice that if
> your expression is a polynomial or rational and you choose your
> points in a "not too special" way, this gives actually a rigorous
> "proof"
> that the expression is 0. In general, this is an extrremely reliable
> heuristic (and of course a "proof" if you do not get 0 for some
> values).
> 
> I encounter the same problem frequently, and this method works
> very well, also to test if two complicated expressions are the same
> or not (guess how :)
> 
> Piero
> 
> 
> 
> 330006 at gmail.com wrote:
> 
>>I have a function which is a sum of many terms which look like this:
>>
>>(2*(B-b)^2 - 2*(A-a)*c*d^2)/(4*b^2*(1-c*2)*d^2)
>>
>>I think the function is actually equal to 0, but I have a hard time in
>>trying to simplify it in Mathematica. Any ideas or commands I should
>>try? Any suggestions in general about simplifying formulas will also
>>be greatly appreciated!
>>
>>Thanks a lot!


Random point evaluation, and various other heuristics, are what lie 
behind the Mathematica predicate Developer`ZeroQ.


Daniel Lichtblau
Wolfram Research


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