From an aeroplane vertically above a straight horizontal road ,the angles of depression of two consecutive milestones on
opposite sides of the aeroplane are observed to be A and B. show that height in miles of aeroplane above the road is
tanA tanB / tanA+tanB
please help me
let the plane be at point A at the particular time.
let the height of the plane from the ground be AB= h miles.
C and D be the two consecutive mile stones therefore CD=1 mile,
such that ∠ACB= A and ∠ADB=B.
now in the right angled triangle ABC,
in the right angled triangle ABD,
adding (1) and (2),
which is the required result.
hope this helps you