passwella.
Menu

WAEC Further Mathematics 2010 Question 2

Question 2

Trigonometry

Find the value of cos(60° + 45°) leaving your answer in surd form

  1. A.(√6 + √2)/4
  2. B.(√3 + √6)/4
  3. C.(√2 − √6)/4
  4. D.(√3 − √6)/4
Show the answer and explanation

Answer: C ((√2 − √6)/4)

Explanation

cos(60° + 45°) = cos60°cos45° − sin60°sin45° = (1/2)(√2/2) − (√3/2)(√2/2) = (√2 − √6)/4.