The distance from the t.v. camera to the rocket increasing at Let be the distance from the camera to the rocket, and the height of the rocket. We have x*x =h*h +(4000)(4000) When h=3000 , x*x=(3000)(3000)+(4000)(4000) , which gives x= 5000 We are told that at that instant,dh/dt 800 ft/s So, at that instant 5000dx/dt =3000(800) and dx/dt=3000(800)/5000 =480 ft/s