       Re: solving nonlinear simultaneous equations

• To: mathgroup at smc.vnet.net
• Subject: [mg97959] Re: solving nonlinear simultaneous equations
• From: dooma50 at hotmail.com
• Date: Thu, 26 Mar 2009 05:24:50 -0500 (EST)
• References: <gqacsu\$jd9\$1@smc.vnet.net> <gqd1qd\$nt1\$1@smc.vnet.net>

```Dear Sjoerd ,

How should I decide the staring values as you gaves 0.5, 0.6, 0.4, 0.8

And these results are only answers?

Because in this model, answers should be t0<t1<t2<t3 basically.

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

BR.
Dooma Casper

On 3=A4=EB25=A4=E9, =A4U=A4=C86=AE=C942=A4=C0, "Sjoerd C. de Vries" <sjoerd=
.c.devr... at gmail.com>
wrote:
> 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- =C1=F4=C2=C3=B3Q=A4=DE=A5=
=CE=A4=E5=A6r -
>
> - =C5=E3=A5=DC=B3Q=A4=DE=A5=CE=A4=E5=A6r -

```

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