Question

The angle of elevation of an airplane from a point on the ground is 600 . After a flight of 30 seconds, the angle of elevation becomes 300 . If the airplane is flying at a constant height of 3000√3 m, find the speed of the airplane. 

Answer 1

Correct figure 

ΔABE, BE/AB = tan 60°

⇒ AB = 3000 m

In Δ DAC, DC/AC = tam 30° 

⇒ AC = 9000 m

BC = AC - AB = 6000m

∴ Speed of aeroplane = 6000/30 m/s = 200 m/s.