How can I solve the error "unable to convert to matrix form because the system does not seem to be linear"

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Sebastián
Sebastián 2023-5-8
移动：Matt J 2023-5-9
I have 19 equations and 19 variables. I am trying to use equations to matrix to solve it, yet I get the error:
Error using mupadengine/feval_internal
Unable to convert to matrix form because the system does not seem to be linear.
Error in sym/equationsToMatrix (line 61)
T = eng.feval_internal('symobj::equationsToMatrix',eqns,vars);
Some of the variables in my equations are squared, for example:
eqn15=(ayAB)+((0.275.*sind(th)).*((OAP).^2))-((0.15.*cosd(th2)).*(al_AB))-((0.15.*sind(th2)).*((AB).^2))==0;
Are those squares the mistake? How could I solve a system of non-linear equations if necessary?

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回答（1 个）

I CHUN LIN
I CHUN LIN 2023-5-8
移动：Matt J 2023-5-9
You can not use matrix if the system is non-linear, maybe try fsolve or vpasolve.
The two-variables system example:
fun = @root2d;
x0 = [0,0];
x = fsolve(fun,x0)
function F = root2d(x)
F(1) = exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);
F(2) = x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5;
end

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