function rhs=order2_rhs(t,u)
%
% function rhs=order2_rhs(t,u)
% where
%    t = time
%    rhs(1) = du(1)/dt = dy/dt = z
%    rhs(2) = du(2)/dt = dz/dt = -4y+sin(At)
%
%    global constant A;

global A;

y = u(1);
z = u(2);

dydt = z;
dzdt = -4*y+sin(A*t);

rhs(1) = dydt;
rhs(2) = dzdt;

rhs=rhs';    % the transpose is required by ode45.m