CBSE Class 10-Mathematics: Chapter –9 Some Applications of Trigonometry Part 10
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Question 16:
An aeroplane flying horizontally at a height of above the ground is observed at a certain point on the earth to subtend an angle of After seconds, its angle of elevation is observed to be . Calculate the speed of aeroplane in .

An Aeroplane Flying Horizontally at a Height
Answer:
Let be the observation point.
Let A be the position of aeroplane such that
Let B be the position of aeroplane after seconds.
In right
In right
Eq.(ii)
Distance covered in 15 seconds
Distance covered in seconds
Question 17:
A man is standing on the deck of a ship which is above water level. He observes the angle of elevation of the top of a lighthouse as and the angle of depression of the base of the lighthouse as .Calculate the height of the lighthouse.

A Man is Standing on the Deck of a Ship
Answer:
Height of lighthouse
In right
In right
In right
Now