maths plse help me..
posted by Meenakshi .
The pilot of an aircraft flying horizontally at a speed of 1200 Km/hr observes an angle of depression of a point on the ground changes from 30 degree to 45 degree in 15 seconds. Find the height of the aircraft at which it is flying?

at 1200km/hr, the plane travels
1200km/hr * 15sec * hr/3600sec = 5km
If the height of the plane is h, and the horizontal distance of the plane from the point on the ground after the 2nd observation is x,
h/x = tan 45° = 1
h/(x+5) = tan 30° = 1/√3
h=x, so,
h/(h+5) = 1/√3
h = 5/(√31) = 6.83 km 
6.83