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MathGroup Archive 1999

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RE: Mathematica can't....

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19831] RE: Mathematica can't....
  • From: gernot at regpro.mechatronik.uni-linz.ac.at (Gernot Grabmair)
  • Date: Sun, 19 Sep 1999 01:20:20 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Leszek wrote:

>Here is the result from Mathematica 4.0
>In[1]:=
>Solve[{p == b^2/a, e == Sqrt[a^2 - b^2]/a}, {a, b}] // InputForm
>
>Out[2]=
>{{b -> (-I*p)/Sqrt[-1 + e^2], a -> -(p/(-1 + e^2))},
> {b -> (I*p)/Sqrt[-1 + e^2], a -> -(p/(-1 + e^2))}}


BUT Mathematica 3.0 can!
{{b -> -(p/Sqrt[1 - e^2]), a -> -(p/(-1 + e^2))},
  {b -> p/Sqrt[1 - e^2], a -> -(p/(-1 + e^2))}}

The other way: try transformation rules (a highlight of mathematica because
you can tell mathematica exactly what it should do. easy like calcul. by
hand.). There are a lot of hintpages in the web dealing with rules.

Gernot Grabmair
Institute of Automatic Control
University of Linz
Austria



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