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MathGroup Archive 2004

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Re: Reduce/Solve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49916] Re: [mg49912] Reduce/Solve
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Fri, 6 Aug 2004 03:09:32 -0400 (EDT)
  • References: <200408051322.JAA05969@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 5 Aug 2004, at 15:22, Dr A.H. Harker wrote:

>
> Dear All,
>          I tend to think of Reduce as a more powerful tool than Solve,
> yet with
>
> eq = J == J0 (1 + r/d) Exp[-r/d]
> ss = Solve[eq, r]
> tt = Reduce[eq, r]
>
>  I get useful output from Solve, but Reduce returns the expression
> unevaluated. What am I missing?  Mathematica 5.0.0.0 under Windows XP.
>
>        Tony
>
>  Dr A.H. Harker
>  Director of Postgraduate Studies
>  Deputy Head, Condensed Matter and Materials Physics Group
>  Department of Physics and Astronomy
>  University College London
>  Gower Street
>  LONDON
>  WC1E  6BT
>  (44)(0)207 679 3404
>  a.harker at ucl.ac.uk
>
>
>
>

Reduce is not "more power full than Solve". If this were true what need 
would there be for Solve? Reduce attempts to give a complete solution 
and when that is impossible it returns no answer. In your particular 
case Solve produces a warning about using Inverse functions and tells 
you that you may not have a complete solution. That tells you exactly 
the reason why Reduce returns the original expression back to you.



Andrzej Kozlowski
Chiba, Japan
http://www.mimuw.edu.pl/~akoz/


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