The bottom of a large theater screen is 9 ft above your eye level and the top of the screen is 30 ft above your eye level. Assume you walk away from the screen (perpendicular to the screen) at a rate of 6 ft/s while looking at the screen. What is the rate of change of the viewing angle \theta when you are 60 ft from the wall on which the screen hangs, assuming the floor is flat? Write an equation relating x and \theta