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 School of Physics, M013 Fax: +61 8 9380 1014 The University of Western Australia (CRICOS Provider No 00126G) 35 Stirling Highway Crawley WA 6009 mailto:paul at physics.uwa.edu.au AUSTRALIA http://physics.uwa.edu.au/~paul