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WAEC Mathematics 1998 Question 28

Question 28

Trigonometry

In sin (X + 30)° = Cos 40°, find X.

  1. A.10°
  2. B.20°
  3. C.50°
  4. D.60°
  5. E.90°.
Show the answer and explanation

Answer: B (20°)

Explanation

sin A = cos B when A + B = 90°, so X + 30 + 40 = 90 and X = 20°.