For a mass m attached to a spring with spring constant, Newton's Second Law says the displacement of the mass, x(t) should obey the differential equation
d^2x/dt^2=-(k/m)(x)(t)
If the mass crosses x=0 at time t=0 then one can show the displacement should be given by a function of the form x(t)=Acos(bt)
Find the second derivative of x(t)=Acos(bt), i.e compute (d^2)x/dt^2 using x(t)=Acos(bt) Do not include x(t) in your answer.
d^2x/dt^2=