An object is attached to a coiled spring. The object begins at its rest position at t = 0 seconds. It is then propelled downward. Write an equation for the distance of the object from its rest position after t seconds, if the amplitude is 7 inches and the period is 1.5 seconds. The equation for the distance d of the object from its rest position is. (Type an exact answer, using it as needed. Use integers or fractions for any numbers in the equation.)