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WAEC Further Mathematics 2010 Question 28

Question 28

Vectors

Find the direction cosines of the vector 4i − 3j.

  1. A.9/100, 27/10
  2. B.117/17, −117/17
  3. C.4/5, −3/5
  4. D.3√10/10, √10/10
Show the answer and explanation

Answer: C (4/5, −3/5)

Explanation

|4i − 3j| = √(16 + 9) = 5. The direction cosines are 4/5 and −3/5.