Week 3 - Solving second order ODEs

clear all
close all
clc

b=0.05;
g=9.81;
l=1;
m=1;


%initial condition 
theta_0=[0;3];

%time points
t_span = linspace(0,20,500);

%solve ODE
[t,results]= ode45(@(t,theta) ode_func(t,theta,b,g,l,m),t_span,theta_0);

plot(t,results(:,1))
hold on
plot(t,results(:,2))
xlabel('time')
ylabel('plot')





function   [dtheta_dt] = ode_func(t,theta,b,g,l,m)

  theta1 = theta(1)
  theta2 = theta(2)
  dtheta1_dt = theta2;
  dtheta2_dt = -(b/m)*theta2-(g/l)*sin(theta1);
  dtheta_dt = [dtheta1_dt;dtheta2_dt];
end