For a massm 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 crossesx=0 at timet=0 then one can show the displacement should be given by a functionof the formx(t)=Acos(bt)

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Find the second derivative ofx(t)=Acos(bt), i.e compute(d^2)x/dt^2 usingx(t)=Acos(bt) Do not includex(t)in your answer.

d^2x/dt^2=