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GCE Mathematics 1990 Question 42

Question 42

Trigonometry

From the top of a building 10m high, the angle of depression of a stone lying on the horizontal ground is 69°. Calculate, correct to 1 decimal place, the distance of the stone from the foot of the building.

  1. A.3.6m
  2. B.3.8m
  3. C.6.0m
  4. D.9.3m
  5. E.26.1m
Show the answer and explanation

Answer: B (3.8m)

Explanation

The angle of elevation of the top from the stone is 69°, so distance = 10/tan 69° = 10/2.605 = 3.84 ≈ 3.8m.