Re: Solving Nonlinear Equations
- To: mathgroup at smc.vnet.net
- Subject: [mg80584] Re: [mg80515] Solving Nonlinear Equations
- From: DrMajorBob <drmajorbob at bigfoot.com>
- Date: Sun, 26 Aug 2007 03:15:12 -0400 (EDT)
- References: <13554088.1187940242361.JavaMail.root@m35>
- Reply-to: drmajorbob at bigfoot.com
That's not a legal syntax (mismatched brackets, etc.), and if it were, you
didn't give the initial values or the values of m1, m2, m3, and m4, so.. .
what can we do?
In addition, C and D are system-defined symbols. FindRoot probably uses D
to take derivatives, so you're just asking for trouble with variable names
like that. I never, never, EVER start one of my own variables with a
capital; that makes it obvious whose symbol it is.
Bobby
On Fri, 24 Aug 2007 00:56:16 -0500, Biyana, D. (Dugmore)
<DugmoreB at Nedbank.co.za> wrote:
>
> I'm using Mathematica V6.0.1 and I have a system of 4 nonlinear equati=
ons
> which I'm trying to solve using FindRoot:
> FindRoot[{m1==C-D*Exp[1/(2*B^2)]*Sinh[A/B],
> m2==C^2+(D^2/2)(Exp[2/B^2]Cosh[2A/B]-1)-2C*D*Exp[1/(2B^2)]*Sinh[A/=
B],
> m3==C^3-3*C^3*D*Exp[1/(2B^2)]*Sinh[A/B],+3*C(D^2/2))*(Exp[2/B^2]Co=
sh[2A/B]-1
> )+(D^3/4)(3*Exp[1/(2B^2)]Sinh[A/B]-Exp[9/(2B^2)]Sinh[3A/B]),
> m4==C^4-4(C^3)D*Exp[1/(2B^2)]*Sinh[A/B]+3(C*D)^2))*(Exp[2/B^2]Cosh=
[2A/B]-1)+
> (D^3/4)+C*D^3(3*Exp[1/(2B^2)]Sinh[A/B]-Exp[9/(2B^2)]Sinh[3A/B])+(D^4/8=
)(Exp[
> 8/(B^2)]*Cosh
> [4A/B]-4*Exp[2/(B^2)]Cosh[2A/B]),{{A,initA},{B,initB},{C,initC},{D,ini=
tD}}]
> I get the message " FindRoot::cvmit : Failed to converge to the reques=
ted
> accuracy..." which I suspect is a result of initial values of A, B,C, =
=
> and D.
> What trick can one use to get accepatble initial values?
> MD Biyana
>
> ********************
> Nedbank Limited Reg No 1951/000009/06. The following link displays the=
=
> names of the Nedbank Board of Directors and Company Secretary. =
> [ http://www.nedbank.co.za/terms/DirectorsNedbank.htm ]
> This email is confidential and is intended for the addressee only. The=
=
> following link will take you to Nedbank's legal notice. =
> [ http://www.nedbank.co.za/terms/EmailDisclaimer.htm ]
> ********************
>
>
>
-- =
DrMajorBob at bigfoot.com