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WAEC Mathematics 1988 Question 30

Question 30

Trigonometry

Cos x is negative and sin x is negative. Which of the following is true of x?

  1. A.0° < x < 90°
  2. B.90° < x < 180°
  3. C.180° < x < 270°
  4. D.270° < x < 360°
  5. E.−90° < x < 90°
Show the answer and explanation

Answer: C (180° < x < 270°)

Explanation

Sine and cosine are both negative only in the third quadrant, 180° < x < 270°.