PLEASE HELP!!
Drop down answers are repeating or terminating

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

True or false: the graph of y=f(bx) is a horizontal compression of the graph y=f(x) if b< 1

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).