Question: An air-traffic controller observes two aircraft on his radar screen. The first is at altitude 900 m, horizontal distance 20.0 km, and 25.5° south of west. The second aircraft is at altitude 1000 m, horizontal distance 17.2 km, and 22.0° south of west. What is the distance between the two aircraft? (Place the x axis west, the y axis south, and the z axis vertical.)