A rocket travels vertically at a speed of 1200 km/hr. The rocket is tracked through a telescope by an observer located 15 km from the launching pad. Find the rate at which the angle between the telescope and the ground is increasing 3 min after the lift-off.
tanθ = h/15
sec^2θ dθ/dt = 1/15 dh/dt
at t=3min = 1/20 hr, h=60 km so tanθ = 4; sec^2θ = 17
17 dθ/dt = 1/15 * 1200
dθ/dt = 80/17 rad/hr