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Re: solving nonlinear simultaneous equations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97902] Re: solving nonlinear simultaneous equations
  • From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
  • Date: Wed, 25 Mar 2009 05:43:34 -0500 (EST)
  • References: <gqacsu$jd9$1@smc.vnet.net>

My guess is that you have been playing with StandardForm and
TarditionalForm formatting. Parts of the expressions like t1(1 - t0)
are internally represented as t1[1 - t0], i.e. t1 is the name of a
function. You can see that if you change the format to InputForm
(using the Cell/Convert tomenu). So, what you must do is change the
square brackets in parenthesis using Finf and Replace.

Additionally, the syntax of your FindRoot is wrong. You cannot have to
starting values. If you rfepaired that and you tweak the starting
values and WorkingPrecision somewhat you get:

FindRoot[{eq0, eq1, eq2, eq3},
 {{t0, 0.5}, {t1, 0.6}, {t2, 0.4}, {t3, 0.8}}, WorkingPrecision -> 50]

{t0 -> 0.042950144337512339004069005918555574390189195213080,
 t1 -> 0.020794416091072412934056566904308358806687991905694,
 t2 -> 0.014356830943135308919996619330315956865348280462553,
 t3 -> -0.29047823800632023417669910887671278352651919604465}

Cheers -- Sjoerd
On Mar 24, 12:33 pm, doom... at hotmail.com wrote:
> I'm using mathematica5.2 to solving 4 complex nonlinear simultaneous
> equations
>
> I'm only need to know the approximate answers,but "FindRoot" keeps
> showing "FindRoot::nlnum" error messages.
>
> How can I solve this problem?
>
> I provides my final_2.nb file by website link.
>
> http://awin.cs.ccu.edu.tw/~dooma/final_2.nb



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