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MathGroup Archive 2003

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Re: reduced functionality of Solve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg44285] Re: reduced functionality of Solve
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Tue, 4 Nov 2003 03:23:58 -0500 (EST)
  • Organization: The University of Western Australia
  • References: <bnnusd$5vc$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

In article <bnnusd$5vc$1 at smc.vnet.net>,
 Andrew Collier <colliera at nu.ac.za> wrote:

> 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.

5.0 is being more careful that 4.1.

> 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
> -------------------------------------------------------------------------

Replace Solve with Reduce. Reduce gives the complete family of 
solutions, including arbitrary constants corresponding to the 
non-uniqueness of the solution.

[However, I note tha FullSimplify in Mathematica 5.0 does not simplify

   2 ArcTan[Sqrt[(1/3) (4 - Sqrt[7])]] 
to 
   ArcTan[Sqrt[6]]]

but it does verify that 

 FullSimplify[Tan[2 ArcTan[Sqrt[(1/3) (4 - Sqrt[7])]]] - Sqrt[6]]

returns 0.]

Cheers,
Paul

-- 
Paul Abbott                                   Phone: +61 8 9380 2734
School of Physics, M013                         Fax: +61 8 9380 1014
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AUSTRALIA                            http://physics.uwa.edu.au/~paul


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