Week 3 - Solving second order ODEs

first i take one second order equation then break into 2 1st order equation.taking all given values.then select time span.then use a inbuild function ode45.i use a function called ode_func.in 2nd programme i write the steps of 2nd order eqution to 1st order equation.

clear all
close all
clc

b=0.05;
g=9.81;
l=1;
m=1;
%initial condition
theta_0=[0;5];
%time span
t_span=linspace(0,10,500);

%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))
ylabel("plot")
xlabel("time")
    


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