the angle of elevation of an aeroplane from a point on the ground is 45 degree. After 15 seconds of flight the angle changes to 30 degree.f the plane is flying at a constant height of 2500m,find the speed of the plane.
Let the initial and final position of the plane be A and B.
Let O be the point of observation.
AA´ and BB´ denote the height of the plane from the ground.
∴ AA´ = BB´ = 2500 m
Distance covered by the plane from A to B is AB or A´B´
⇒ A´B´ = OB´ – OA´
Time taken by the plane in moving from A to B = 15 seconds
Speed of the plane