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WAEC Mathematics 1998 Question 26

Question 26

Trigonometry

In ΔPQR, ∠PQR is a right angle. |QR| = 2cm and ∠PRQ = 60°. Find |PR|.

  1. A.4√3cm
  2. B.4cm
  3. C.2√3cm
  4. D.4/3cm
  5. E.1cm.
Show the answer and explanation

Answer: B (4cm)

Explanation

QR is adjacent to the 60° angle: cos 60° = QR/PR, so PR = 2 ÷ ½ = 4 cm.