Re: solving nonlinear simultaneous equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg97998] Re: solving nonlinear simultaneous equations*From*: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>*Date*: Fri, 27 Mar 2009 05:37:29 -0500 (EST)*References*: <gqacsu$jd9$1@smc.vnet.net> <gqd1qd$nt1$1@smc.vnet.net>

As far as I know FindRoot stops at the first answer it gets. I tried a few starting points. The answer below is correct: just fill in these values and you'll see they're right. There are quite probably more correct solutions. Try filling in some other starting values. Cheers -- Sjoerd On Mar 26, 12:23 pm, doom... at hotmail.com wrote: > 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} > > Thanks for your reply > > BR. > Dooma Casper > > On 3=A4=EB25=A4=E9, =A4U=A4=C86=AE=C942=A4=C0, "Sjo= erd 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 -