A mountain is due north and the peak is 20°
above the horizon (the angle between a level line drawn straight north and a
line drawn to point at the peak is 20°). You walk 1000 feet due east and the
mountain is now 10° west of north (you have to rotate 10° counterclockwise from
facing north to be facing the peak). How tall is the mountain? Note that the
ground is level as you walk east and we are assuming the earth is flat.