function yprime = InvPend(t,y)
% Usage: yprime = InvPend(t,y)
%
% This function defines the inverted pendulum differential equation
% transformed from the second order ode.
%
% Variables;
%   t     time, scalar
%   y     a 2-vector, where
%
%		y(1) = theta(t) and y(2) = (d/dt)theta(t)
%
%	where theta(t) is the angle in the inverted pendulum problem.l

% parameters
global L;
global A;
global w;
% constant, gravitation
global g;

yprime(1,1) = y(2);
yprime(2,1) = 3*(g - A*w*w*sin(w*t))*sin(y(1))/(2*L);