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WAEC Further Mathematics 2009 Question 37

Question 37

Vectors

Express the force F = (8N, 150°) in the form (ai + bj) where a and b are constants.

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

Answer: D (−4√3i + 4j)

Explanation

Measuring 150° anticlockwise from the positive x-axis: a = 8 cos 150° = −4√3 and b = 8 sin 150° = 4, so F = −4√3i + 4j.