A 2.2m tall girl spots an aeroplane moving with the wind in a horizontal line at a height of 86.2m from the ground

A 2.2m tall girl spots an aeroplane moving with the wind in a horizontal line at a height of 86.2m from the ground. The angle of elevation of the aeroplane from eyes of the girl at instant is 60°. After some time, the angle of elevation reduces to 30°. Find the distance travelled by the aeroplane during the interval?

(a) 84√3 m

(b)  56√3m

(c)  70√3m

(d) 56m

Sol:

In ∆ ACD

AD = 84m

tan60° =AD/CD