A telescope is placed on a tower 400 m away from a crossing. To have a direct view of the crossing, the telescope has to be bent at an angle 15 degrees to the horizontal.
Let the height of the tower be H. The height H and the distance 400 m are related by the trigonometric identity tan 15 = H/400
=> H = 400*tan 15
=> H `~~` 107.17
The height of the tower is approximately 107.17 m