The angle of depression is 30°
Explanation:
The building height= 20ft.
The distance from the building the cable is attached to the ground = 35ft.
Let the angle at the top of the building be 'a'
Refer the diagram.
We can say that,
a° + angle of depression= 90°
Tan a° = opposite side/ adjacent side
Tan a° = 35/20
Tan a° = 7/4
Tan a° = 1.75
Tan 60° = 1.75
Tan a° = tan 60°
a° = 60°
So the angle of depression= 90° - 60°
Angle of depression= 30°