how to Nonlinear equations?(two variables)

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

[darova]

Did you try something? I think you need fsolve and for loop. Solve equations for every t step

Answer 1

[Are Mjaavatten]

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')

[semih kahraman]

I want to find i1 i2 i3 and want to plot their changes. with subplot

[Are Mjaavatten]

The correct expression for A is:

A = [14+R1(t(i)),-10,-4;-10,18+R2(t(i)),1;-4,-8,12];

If you use this in my code, then i1 = X(1,:) and so on. The plot command should give a plot of all three currents versus t. To see which is which:

legend('i1(t)','i2(t)','i3(t)','location','west');
xlabel t

Plotting them in separate subplots should be trivial.

[semih kahraman]

thank you for your interest. I just started learning.what I want to do is print these three streams on different screens one after another. I want to do this with a subplot. at the same time, the initial values ​​of my i are 0. and t = 0: 0.01: 5.

and I want to find the average values ​​of these works.

thank you again for your interest.

[Are Mjaavatten]

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,:))));

[semih kahraman]

thank you so much sir