how to Nonlinear equations?(two variables)

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semih kahraman
semih kahraman 2020-5-2
编辑： semih kahraman 2020-5-3
f(1) = x(1)*(14+r1)-10*x(2)-4*x(3)-100;
f(2) = x(1)*-10+x(2)(18+r2)+x(3)*-8+80;
f(3) = x(1)*-4+x(2)*-8+x(3)*12-50;
how can I solve these nonlinear equations. There are rheostatic values so there is a second variable t. Should I write a function?eq
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darova
darova 2020-5-2
Did you try something? I think you need fsolve and for loop. Solve equations for every t step

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Are Mjaavatten
Are Mjaavatten 2020-5-2
Although R1 and R2 are nonlinear finctions of t, your equations are linear in x. So you write the equations on the form
A(t)*x = b and solve by x = A\b for every t of interest.
I suggest you define R1(t) and R2(t) as anonymous functions. Here is a template:
R1 = @(t) 5*t^2+10;
R2 = @(t) 2*exp(t)+5;
t = linspace(0,5);
b = [100;-80+8;50];
X= zeros(3,length(t));
for i = 1:length(t)
A = [3 by 3 matrix containing R1(t(i)) and R2(t(i))];
X(:,i) = A\b;
end
plot(t,X')
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Are Mjaavatten
Are Mjaavatten 2020-5-3
figure;
subplot(311);
plot(t,X(1,:));
title(sprintf('I_1 Mean value:%f',mean(X(1,:))));
subplot(312);
plot(t,X(2,:));
title(sprintf('I_2 Mean value:%f',mean(X(2,:))));
subplot(313);
plot(t,X(3,:));
title(sprintf('I_3 Mean value:%f',mean(X(3,:))));

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