Elevator 0>0 Observer An observer is 25 m above the ground floor of a large hotel atrium looking at a glass-enclosed elevator shaft that is 15 m horizontally from the observer (see figure). The angle of elevation of the elevator is the angle that the observer's line of sight makes with the horizontal (it may be positive or negative). Assuming that the elevator rises at a rate of 4 m / s, what is the rate of change of the angle of elevation when the elevator is 20 m above the ground? When the elevator is 40 m above the ground? 25 m Write an equation relating the angle, 0, and the vertical distance between the height of the elevator and the height of the observer, H. tan 0 = = H 15 Differentiate both sides of the equation with respect to t. do dH dt 15 sec -0 dt When the elevator is 20 m above the ground, the rate of change of the angle of elevation is (Type an exact answer in simplified form.) When the elevator is 40 m above the ground, the rate of change of the angle of elevation is (Type an exact answer in simplified form.)