Fweee points sin25 +cos25 ∘ sin65 ∘=sin25 sin(90 ∘−65 ∘ )+cos25 ∘cos(90 ∘−65 ∘ )=sin25∘sin25 ∘+cos25 ∘cos25 =sin 2 25 ∘ +cos 2 25 ∘=1
injoy

Amass weighing 16 pounds stretches a spring 8/3 feet. the mass is initially released from rest from a point 2 feet below the equilibrium position, and the subsequent motion takes place in a medium that offers a damping force that is numerically equal to 1/2 the instantaneous velocity. find the equation of motion if the mass is driven by an external force equal to f(t)=cos(2t).