MATLAB: Using ODE45 to solve a system of 2nd order ODEs equation

ode45

I am trying to solve
This is what I have written as my finction script. everytime I try to solve it once I type the initial condiitions to the Command Windown, I get "Show complete stack trace." How can I solve my problem?
function theta_dot = pendulum(t,x)
theta_dot = [x(2);
             -8.8*x(1)-1.8*x(3);
             x(4);
             1.8*x(1)+8.8*x(3)];
end

Best Answer

After fixing the sign-errors in your ODE-function this:
thetathetadot0 = [0 0 0 -1];
[t,theta] = ode45(@(t,y) pendulum(t,y),0:0.1:10,thetathetadot0);
plot(t,theta)
works just fine.
HTH
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