Re: AW: Infrequent Mathematica User
- To: mathgroup at smc.vnet.net
- Subject: [mg47071] Re: AW: Infrequent Mathematica User
- From: Paul Abbott <paul at physics.uwa.edu.au>
- Date: Tue, 23 Mar 2004 01:58:18 -0500 (EST)
- Organization: The University of Western Australia
- References: <c3oc0r$8fe$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <c3oc0r$8fe$1 at smc.vnet.net>, Matthias.Bode at oppenheim.de
wrote:
> applying the KIS principle, try:
>
> Clear[x, y, z]
> func = x/(1 + x^2) +
> y/(1 + x^2 + y^2) +
> z/(1 + x^2 + y^2 + z^2);
> dfx = D[func, x];
> dfy = D[func, y];
> dfz = D[func, z];
> Reduce[dfx == 0 &&
> dfy == 0 && dfz == 0, x]
> N[%]
Alternatively, one can use the built-in Del operator (which formats
nicely in StandardForm or TraditionalForm):
f[x_, y_, z_] = x/(x^2 + 1) + y/(x^2 + y^2 + 1) +
z/(x^2 + y^2 + z^2 + 1);
Del[f_] := {D[f, x], D[f, y], D[f, z]}
Reduce solves the equations (in terms of Root objects):
Reduce[Del[f[x, y, z]] == 0, x]
NSolve yields high-precision numerical solutions directly:
NSolve[Del[f[x, y, z]] == 0, {x, y, z}, WorkingPrecision -> 20]
Cheers,
Paul
--
Paul Abbott Phone: +61 8 9380 2734
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