Question

An aeroplane is flying horizontally at the height of 1500√3m abov the ground is observed at a certain point on earth to subtend an angle of 60°.after 15 seconds ,its angle of elevation at the same point is observed to be 30°.calculate th speed of the aeroplane in km/hr

Answer 1

Let AC be the height of the plane
Then AC=ED (same height)
Let the speed of plane be X m/s..(note that we are taking speed in m/s.) Then to calculate the distant CD
speed = distance/time
X=distance/15. (time given is 15 seconds)
distance=15x
hence CD is equal to 15x
Now ,
applying tan 60° in triangle ABC
tan 60° =AC/BC
√3=1500√3/BC
BC=1500√3/√3
BC=1500m
Now applying tan 30 in triangle BED
tan30° = ED/BD
tan30°=ED/BC+CD
1/√3=1500√3/1500+15x
X=200
Now we need to change speed in kmph
To do so...200×18/5
720kmph
Answer --- 720 kmph

Answer 2

Answer:

720 km/hr...

Step-by-step explanation:

Hope it helps you...