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