i have function L and initial values phi1 ,phi2 and seta . I want to be derivative this function and equal it by zero for getting the estimated values of these initial values. but showing the next error .what to do?

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mohammed elmenshawy 2016-12-23

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https://ww2.mathworks.cn/matlabcentral/answers/317954-i-have-function-l-and-initial-values-phi1-phi2-and-seta-i-want-to-be-derivative-this-function-a

编辑： John D'Errico 2016-12-27

syms phi1 phi2 seta
L=- ((38*phi1)/281 - (89*phi2)/902 + (149*seta)/1124 - 83/28)^2/8; % function
phi1=0.3; % initial point
phi2=0.5; % initial point
seta=0.4; % initial point
phi1hat=fzero(L,phi1);
phi2hat=fzero(L,phi2); 
setahat=fzero(L,seta);
Error using fzero (line 167)
If FUN is a MATLAB object, it must have an feval method.

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mohammed elmenshawy 2016-12-24

A summary of what I want to do . i have function of 3 parameters L=f(phi1,phi2,seta). i need differential this function with respect to phi1 , phi2 and seta , and equality to zero. Hence we get three equations in three parameters , Give initial values of the three parameters.In the first equation, which is where the differentiation for phi1 we substitute only about phi2 and seta to get phi1 value . By this logic with the phi2 and seta . what to do ?

John D'Errico 2016-12-27

编辑：John D'Errico 2016-12-27

Note that you were trying to solve a 3-dimensional problem, by calling fzero, a 1-d solver, three times. Sorry, but that makes no sense. Use fsolve preferentially, or lacking that, you can use fminsearch if used properly.

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