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WAEC Further Mathematics 2008 Question 30

Question 30

Vectors

Express r = (12, 210°) in the form ai + bj

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

Answer: B (6(−i − √3j))

Explanation

Read 210° as a bearing (clockwise from north): a = 12 sin 210° = −6 and b = 12 cos 210° = −6√3, so r = −6i − 6√3j = 6(−i − √3j).