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MathGroup Archive 2003

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reduced functionality of Solve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg44222] reduced functionality of Solve
  • From: Andrew Collier <colliera at nu.ac.za>
  • Date: Wed, 29 Oct 2003 03:34:05 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

hello,

this may be a naive idea but i expected the functionality of software to
improve with later releases. this, in my opinion, does not seem to be the
case from mathematica 4.1 to 5.0... or maybe i am just missing something.

in a script i have the following bit of code:

-------------------------------------------------------------------------
F[W_, y_] := Exp[-W(Cos[y]^2/Tp + Sin[y]^2/Tn)]

Tn = 3000;
Tp = 2000;

Solve[{D[F[W, y], y] Tan[y] == 2 F[W, y], W == 1000 Sec[y] ^ 2}, {W, y}];
N[%] // TableForm
-------------------------------------------------------------------------

now, with mathematica 4.1 this gives:

-------------------------------------------------------------------------
InverseFunction::ifun: 
   Inverse functions are being used. Values may be lost for multivalued
    inverses.

Solve::ifun: Inverse functions are being used by Solve, so some solutions may
     not be found.

In[5]:= 
Out[5]//TableForm= W -> 7000.   y -> -1.95839

                   W -> 7000.   y -> 1.95839

                   W -> 7000.   y -> -1.1832

                   W -> 7000.   y -> 1.1832
-------------------------------------------------------------------------

which is useful and the kind of result i am after. however, after
upgrading to mathematica 5.0 the same bit of code gives:

-------------------------------------------------------------------------
Solve::tdep: The equations appear to involve the variables to be solved for in
    an essentially non-algebraic way.

In[5]:= 
-------------------------------------------------------------------------

now i read in the manual that Solve "deals primarily with linear and
polynomial equations", but i would expect that if i got a useful answer
with 4.1 i should get the same (or better!) with 5.0.

is there some way of getting the old behaviour with the newer version of
mathematica?

many thanks and best regards,
andrew collier.

-- 
Andrew B. Collier
Antarctic Research Fellow                         tel: +27 31 2601157
Space Physics Research Institute                  fax: +27 31 2616550
University of Natal, Durban, 4041, South Africa


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