Efficient way to solve this (nonlinear) equation?

Question

Amit Kumar 2014-2-21

0
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https://ww2.mathworks.cn/matlabcentral/answers/117021-efficient-way-to-solve-this-nonlinear-equation

回答： Walter Roberson 2014-2-21

Hello all, I want to solve a nonlinear equation but don't know efficient way to do it in Matlab. Can anyone suggest a good way? Here is my code:

G12=7000; 
phi=2*pi/180;
syms gamma_6
tau_6= G12*(gamma_6-20*(gamma_6)^2);
sigma_x= -tau_6/(phi+gamma_6);
sigma_1=vpa(diff(sigma_x,gamma_6));
f=matlabFunction(sigma_1);

I want to solve expression sigma_1=0; sigma_1 is function of gamma_6. What I can do is solve till

sigma_1=vpa(diff(sigma_x,gamma_6));

Then copy entire string to solve('.....=0',gamma_6) However this is not most efficient way. I tried fsolve(f,..) but problems with algorithm. Any suggestions most appreciated. Thanks!