function y = X4DOT(u)
X3 = u(1);
X2DOT = u(2);
L = 0.6; % panjang batang pendulum [m]
M = 0.25; % berat kereta [kg]
m = 0.1; % berat pendulum [kg]
g = 10; % percepatan gravitasi [m/sec2]
y = ((g*sin(X3)) - (X2DOT*cos(X3)))/L;