In the diagram, let H be Mr. Gournic's House, L be his letterbox, and P be the telephone pole.

By alternate angles on parallel lines, we can deduce various other angles in the diagram.

After filling in several angles, we note that , so the paths actually form a right angled triangle .

Then, by Pythagoras' Theorem,

So the distance from his door to the pole is m.

Next, to find the beaing of H from P, note that

, so

Now, note that by alternate angles on parallel lines,

So , approximately.

Therefore the bearing to H from P is , or, if you prefer,