Answer:
11.3°
Explanation:
Refer the attached figure .
Height of building i.e. AB = 160 feet.
A helicopter takes off from the ground 800 feet from the base of a building i.e. BC = 800 ft.
We are required to find what angle did the helicopter take off from i.e. ∠ACB
We will use trigonometric ratio .







Thus the angle at which the helicopter take off from is 11.3°