Draw a right triangle with the right angle at the foot of the tower. The interior angle of the triangle at the top is the complement of the angle of depression. 90 - 74 = 16; it measures 16°. The leg at the bottom has length x. The height of the tower is the vertical leg and is 90 ft. We are looking for x.
For the 16° angle, x is the opposite leg, and 90 ft is the adjacent leg.
