Answer:
7949.13 feet
Explanation:
We are given that,
Angle of depression from the spot to the group = 39°
Height of Grand Canyon = 5000 feet.
So, we will get the following figure of a right triangle.
As, 'in a right triangle, the angles and the sides can be written in trigonometric form'.
We get,

i.e.

i.e.

i.e.

i.e. x = 7949.13 feet
Thus, the line of sight distance is 7949.13 feet.