passwella.
Menu

WAEC Further Mathematics 2023 Question 40

Question 40

Trigonometry

Given that sin x = 4/5 and cos y = 12/13, where x is an obtuse angle and y is an acute angle, find the value of sin (x − y)

  1. A.16/65
  2. B.48/65
  3. C.56/65
  4. D.63/65
Show the answer and explanation

Answer: D (63/65)

Explanation

x obtuse: cos x = −3/5; y acute: sin y = 5/13. sin(x − y) = (4/5)(12/13) − (−3/5)(5/13) = 48/65 + 15/65 = 63/65.