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GCE Mathematics 1989 Question 47

Question 47

Trigonometry

If sin θ = ½ and cos θ = −√3/2, what is the value of θ?

  1. A.30°
  2. B.60°
  3. C.90°
  4. D.120°
  5. E.150°
Show the answer and explanation

Answer: E (150°)

Explanation

Sine positive and cosine negative puts θ in the second quadrant; the reference angle is 30°, so θ = 180° − 30° = 150°.