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WAEC Mathematics 1992 Question 29

Question 29

Trigonometry

Sin 60° has the same value as I. sin 120° II. cos 240° III. −sin 150° IV. cos 210° V. sin 240°

  1. A.I only
  2. B.II only
  3. C.IV only
  4. D.III only
  5. E.IV and V only
Show the answer and explanation

Answer: A (I only)

Explanation

sin 60° = √3/2. sin 120° = sin 60° = √3/2; cos 240° = −½, −sin 150° = −½, cos 210° = −√3/2 and sin 240° = −√3/2. Only I matches.