Question

a tunnel under a river is 196.8 ft below the surface at its west point. if the angle of depression of the runnel is 4.962 then how far apart on the surface are entrances to the tunnel? how long is tunnel

Answer 1

Assume a V-shaped profile,with the low point in the middle of the tunnel. If the tunnel length is L,
tan 4.962 = 196.8 ft/(L/2)
0.08682 *L/2 = 196.8
Solve for L

Answer 2

4533.51