Find the solution of a system of two nonlinear, complicated equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg108815] Find the solution of a system of two nonlinear, complicated equations*From*: "Christian Schneider" <kofferpc at gmx.net>*Date*: Thu, 1 Apr 2010 06:02:21 -0500 (EST)

Dear members of the mathgroup email group, I have serious difficulties in solving the following problem in Mathematica v.7 and would very grateful if anyone could give me a helping hand with that. I want to solve a system of two nonlinear equations. Unfortunately the equations are rather bulky. I've tried to use FindRoot for this problem, but I get three error messages: General::ovfl : Overflow occurred in computation General::ovfl : Overflow occurred in computation FindRoot::nlnum : The function value {Overflow[], Overflow[]} is not a list of numbers with dimensions {2} at {sigmabare, dmu}={0.2, 4}. I think mathematica is telling me that the iterations or the starting points need to be changed. I tried to do that, but always end up with that error messages. I have a set of two equations with two variables and two parameters each, and I want to solve the two variables of the set. The variables of the two equations are: sigmabare, dmu The two parameters per equation are for equation1: epsilon1, c01 for equation2: epsilon2, c02 The complete syntax as plain text is: FindRoot[{c01*6.022*10^(23) == Abs[sigmabare/(2*(437*10^(-12))*3*(1.602*10^(-19)))]* Exp[(-(4.11641*10^(-21))*(1.65*(1/(4*(4.11641*10^(-21))* epsilon1*(8.854*10^(-12)))*((1.602*10^(-19))^3*3^\ 3*sigmabare/3.141592654)^(1/2)) - 2.61*(1/(4*(4.11641*10^(-21))* epsilon1*(8.854*10^(-12)))*((1.602*10^(-19))^3*3^\ 3*sigmabare/3.141592654)^(1/2))^(1/4) + 0.26*Log[ 1/(4*(4.11641*10^(-21))* epsilon1*(8.854*10^(-12)))*((1.602*10^(-19))^3*3^\ 3*sigmabare/3.141592654)^(1/2)] + 1.95))/((4.11641*10^(-21)))]* Exp[dmu/((4.11641*10^(-21)))]/(6.022*10^(23)) /. c01 -> {0.5*10^(-5)} /. epsilon1 -> {54} , c02*6.022*10^(23) == Abs[sigmabare/(2*(437*10^(-12))*3*(1.602*10^(-19)))]* Exp[(-(4.11641*10^(-21))*(1.65*(1/(4*(4.11641*10^(-21))* epsilon2*(8.854*10^(-12)))*((1.602*10^(-19))^3*3^3* sigmabare/3.141592654)^(1/2)) - 2.61*(1/(4*(4.11641*10^(-21))* epsilon2*(8.854*10^(-12)))*((1.602*10^(-19))^3*3^3* sigmabare/3.141592654)^(1/2))^(1/4) + 0.26*Log[ 1/(4*(4.11641*10^(-21))* epsilon2*(8.854*10^(-12)))*((1.602*10^(-19))^3*3^3* sigmabare/3.141592654)^(1/2)] + 1.95))/((4.11641*10^(-21)))]* Exp[dmu/((4.11641*10^(-21)))]/(6.022*10^(23))} /. c02 -> {1*10^(-5)} /. epsilon2 -> {78}, {{sigmabare, 0.2}, {dmu, 4}}] Sorry for this mess of equations. Has somebody an idea where I am going wrong and how to solve this? Thanks a lot in advance for your help, Chris