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JAMB Mathematics 1983 Question 46

Question 46

Trigonometry

In triangle PQR, QR = 3cm, PR = √3cm, PQ = 2√3cm and PQR = 30°. Find angles P and R.

  1. A.P = 60° and R = 90°
  2. B.P = 30° and R = 120°
  3. C.P = 90° and R = 60°
  4. D.P = 60° and R = 60°
  5. E.P = 45° and R = 105°.
Show the answer and explanation

Answer: A (P = 60° and R = 90°)

Explanation

PR² + QR² = 3 + 9 = 12 = PQ², so R = 90°. Then P = 180° − 90° − 30° = 60°.