An aircraft is spotted by observers and who are feet apart.

As the aircraft passes over the line joining them, each observer takes a sighting of the angle

of elevation to the plane, as indicated in the figure.

\ \

Height of the aircraft :

The height can be calculated from either side by using  to place where plane is.

Since the height will be the same for both observers, set both equations equal.

Consider the distance between observer and aircraft is .

Then distance to plane from the other observer is .

Therefore

Therefore, the distance is .

The aircraft is high.