Home › UP Board Class 10 › mathematics › Some Applications of Trigonometry › The angle of elevation of a cloud from a point 6…
The angle of elevation of a cloud from a point 60 m above a lake is 30 degrees and the angle of depression of its reflection is 60 degrees. The height of the cloud above the lake is
A100 m
B110 m
C120 m
D150 m
Answer & Solution
Correct answer: C. 120 m
1. Let cloud be h m above lake; reflection is h m below lake. From the observation point 60 m above lake:
2. tan(30) = (h - 60)/d, tan(60) = (h + 60)/d.
3. Divide: tan(60)/tan(30) = (h + 60)/(h - 60) = 3, giving h = 120 m.
_Source: NCERT Class 10 Mathematics, Ch 9 "Some Applications of Trigonometry", §9.2_
Related questions
From the top of a 7 m building, the angles of elevation of the top and angle of depressionThe shadow of a 30 m tall tower becomes 30/(square root of 3) m shorter when the sun risesFrom the top of a 10 m tower, the angle of depression of an object on the ground is 60 degA man standing on the deck of a ship 8 m above water level observes the angle of elevationThe angle of elevation of the top of a building from the bottom and top of a tower are 60 The angles of elevation of the top of a tower from two points A and B at distances of 4 m A tree breaks due to a storm and the broken part bends so that its top touches the ground An aeroplane at an altitude of 1500 m makes an angle of depression of 60 degrees with a fi