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WAEC Mathematics 2004 Question 3

Question 3

Trigonometry

Given that sin (5x − 28)° = cos (3x − 50)°, 0 < x < 90°, find the value of x.

  1. A.14°
  2. B.21°
  3. C.32°
  4. D.39°
Show the answer and explanation

Answer: B (21°)

Explanation

sin A = cos B when A + B = 90°: 5x − 28 + 3x − 50 = 90, so 8x = 168 and x = 21°.