Solving multiple nonlinear equations

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Fan
Fan on 16 Sep 2014
Edited: Matt J on 16 Sep 2014
Hi,
I have five nonlinear equations, and I am trying to solve for five unknowns. No answers were found when I tried to use fsolve in MatLab and Findroot in Mathematica. However, when I tried to manipulate the equations in Mathematica, those five lines (equations) do seem to intercept at a certain point. When I used those values as my initial guess for fsolve or findroot, there is no valid answers... Any idea?
Also, I do know what value ranges these unknowns need to be, but how do you have fsolve search in a range?
Thanks for the help!
  2 Comments
Image Analyst
Image Analyst on 16 Sep 2014
How about you give us the equations?
Fan
Fan on 16 Sep 2014
These five nonlinear equations are very long...

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Answers (1)

Matt J
Matt J on 16 Sep 2014
Edited: Matt J on 16 Sep 2014
To use fsolve, you had to provide a function F(x) with the aim of solving F(x)=0. What value do you get for F(xi) where xi is the "intercept" point that you obtained from Mathematica? How far from 0 is it?
If the intercept point really is a solution in Mathematica, as you seem to be saying, there is no reason it shouldn't also be a solution in MATLAB if you've implemented the equations correctly. Looking at F(xi) should be a straightforward way of checking this.

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