Question

A plane is flying due east at 600 km/h at a constant altitude. From an observation point P on the ground, the plane is sighted on a bearing of 320◦. One minute later, the bearing of the plane is 75◦ and its angle of elevation is 25◦.

Show that the altitude h metres of the plane is given by h =
(10 000 sin 50◦ tan 25◦)/(sin 65◦)

and hence find the altitude, correct to the nearest metre