function y = x4dot(x)
g=10; % gravitasi [m/sec2]
l=0.5; % panjang pendulum [m]
M=0.25; % Massa Kereta [kg]
m=0.05; % massa bob pendulum [kg]
x3=x(1); % sudut pendulum [radian]
x2dot=x(2); % percepatan kereta [m/sec2]
y=((g*sin(x3)) - (x2dot*cos(x3)))/l;