Re: Solving Nonlinear Equations
- To: mathgroup at smc.vnet.net
- Subject: [mg80560] Re: Solving Nonlinear Equations
- From: "fkampas" <fkampas at verizon.net>
- Date: Sun, 26 Aug 2007 03:02:44 -0400 (EDT)
- References: <fals2t$g7g$1@smc.vnet.net>
Use NMinimize with an objective function of 0 and your equations as constraints. This should work better since NMinimize is a global optimizer. "Biyana, D. (Dugmore)" <DugmoreB at Nedbank.co.za> wrote in message news:fals2t$g7g$1 at smc.vnet.net... > > I'm using Mathematica V6.0.1 and I have a system of 4 nonlinear equations > 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]Cosh[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,initD}}] > > I get the message " FindRoot::cvmit : Failed to converge to the requested > 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 ] > ******************** > >