Question

an aeroplane flying horizontally 1 km above the ground is observed at the elevation of 60°.after 10 seconds it's elevation is observed to be 30 degree find the speed of the aeroplane .

Answer 1

Here, A is the point on the ground whereas C and D are position of the aeroplane.

In ∆CBA,



In ∆DEA,



Here, BE = AB – AE



BE is the distance travelled by the plane in 10 sec.



= 360() km/h 

= 240 km/h