Solving second order ODEs

% 2nd order ordinary differential equation (ODE)
clear all
close all
clc

b = 0.05; % damping co-efficient
m = 0.1; % mass - kg
g = 9.81; % gravity - m/(s^2)
l = 1; % length - meter (m)

% 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)

i = 1

figure(1)

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

for i = l:length(t)

x = (sin(results(i,1)))
y = (-cos(results(i,1)))

figure(2)
plot([0, x],[0, y],'-o')
axis ([-1 1 -2 0])
text(0, -1.6, ['time', num2str(t(i,1))])
M(i) = getframe(gcf);
pause(0.1)
end