math
posted by Sasuke .
From a mountain 1780 ft. high, the angle of depression of a point on the nearer shore of a river is 48 degrees 40 minutes and of a point directly across on the opposite side is 22 degrees 20 minutes. What is the width of the river between the two points?

If you draw a diagram, you will see that you cannot compute the width of the river without knowing how far the river is from the mountain.

If we assume that the river is at the same elevation of the base of the mountain, then
Width of the river
=distance of far shore  distance of near shore
=1780/tan(θ2)1780/tan(θ1)