Question

An aeroplane is flying horizontally, 2000 m above
the ground and is going away from an observer on
a level ground. At a certain instant, the observer
finds that the angle of elevation of the plane is 63º.
After 15 seconds, its elevation from the same point
changes to 37º. Find the speed of the aeroplane in
km per hour.
please answer step wise its from the chapter heights and distances. ​

Answer 1

Step-by-step explanation:

In ∆ADC

tan37= AD/AC

3/4=2000/AC

AC=(2000×4)/3

AC= 8000/3=2666.66

IN ∆BEC

tan63= BE/EC

12/5=2000/EC

EC=(2000×5)/12

EC= 833.33

NOW ,

AC= EC + DE

2666.66=833.33 + DE

DE= 1833.33

speed = distance/time

=1833.33/15

=122.222 m/s

speed in km/h= (122.22×1000)/60×60

= 33.95km/h