Assume a flat Earth.Originally Posted byphgao

The depression angles tell you the horizonal range to each buoy, as:

Their bearings are the angles between North and the direction of the buoy

measured in the horizontal plane. So the difference in bearings gives

the angle between the lines joining the foot of the cliff to each of the

buoys.

So now you have two sides of a triangle (the two horizontal ranges), and

the angle between them (the difference in the bearings). If you now solve

for the third side of this triangle you will have the distance between the

two buoys.

RonL