Ngles α and β are angles in standard position such that:
α terminates in quadrant iii and sinα = -5/13
β terminates in quadrant ii and tanβ = -8/15
find cos(α - β).
-220/221
-140/221
140/221
220/221

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).