function y = x4dot(x)
g=10; % gravitasi
l=0.28; % panjang pendulum
M=0.11; % massa kereta
m=0.03; % massa pendulum
x3=x(1);
x4=x(2);
u=x(3);
A=m*l*x4*x4*sin(x3)*cos(x3);
B=(M+m)*g*sin(x3);
C=u*cos(x3);
D=m*l*cos(x3)*cos(x3);
E=(M+m)*l;
y=(A-B+C)/(D-E);