From the top of a fire tower, a forest ranger sees his partner on the ground at an angle of depression of 40º. If the tower is 45 feet in height, how far is the partner from the base of the tower, to the nearest tenth of a foot? (Detailed explanation please)

Answer 1

Assuming the ground and horizontal are parallel, the angle from the ground at the partner up toward the ranger on the tower is also 40 degrees.
Now you have a right triangle and the side opposite the 40 degrees at the partner is the 45 foot tower so
tan 40 = 45 / d
d = 45 / tan 40