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WAEC Mathematics 1991 (August) Question 24

Question 24

Latitude and Longitude

Two towns, P and Q, are on (4°N 40°W) and (4°N 20°E) respectively. What is the distance between them, along their line of latitude? (Give your answer in terms of π and R, the radius of the earth).

  1. A.2πRcos4°
  2. B.πR sin 40°
  3. C.(πR/2) cos 4°
  4. D.(πR/3) cos 4°
  5. E.(πR/6) sin 4°
Show the answer and explanation

Answer: D ((πR/3) cos 4°)

Explanation

Difference in longitude = 40° + 20° = 60°. Distance = 60/360 × 2πR cos 4° = (πR/3) cos 4°.