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A man on a 10 m cliff observes a boat at an angle of depression of 30 degrees. The distance of the boat from the foot of the cliff is
A10 m
B10 (square root of 3) m
C20 m
D5 (square root of 3) m
Answer & Solution
Correct answer: B. 10 (square root of 3) m
1. tan(30) = 10 / d.
2. d = 10 / tan(30) = 10 × (square root of 3) = 10 (square root of 3).
3. Hence the boat is 10 (square root of 3) m away.
_Source: NCERT Class 10 Mathematics, Ch 9 "Some Applications of Trigonometry", §9.2_
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