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WAEC Mathematics 2003 Question 18

Question 18

Trigonometry

In ΔPQR, ∠PQR = 84°, ∠QPR = 43° and |PQ| = 5cm. Find |QR| in cm, correct to 1 decimal place.

  1. A.3.4
  2. B.4.3
  3. C.5.9
  4. D.6.2
Show the answer and explanation

Answer: B (4.3)

Explanation

∠R = 180 − 84 − 43 = 53°. Sine rule: QR = 5 sin 43°/sin 53° = 5 × 0.6820/0.7986 ≈ 4.3 cm.