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WAEC Further Mathematics 2018 Question 36

Question 36

Statics

Find the angle between forces of magnitudes 7 N and 4 N if their resultant has a magnitude of 9 N.

  1. A.39.45°
  2. B.73.40°
  3. C.75.34°
  4. D.106.60°
Show the answer and explanation

Answer: B (73.40°)

Explanation

9² = 7² + 4² + 2(7)(4) cos θ, so 81 = 65 + 56 cos θ, cos θ = 16/56 and θ ≈ 73.40°.