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WAEC Further Mathematics 2010 Question 13

Question 13

Coordinate Geometry

Calculate, correct to one decimal place, the acute angle between the lines 3x − 4y + 5 = 0 and 2x + 3y − 1 = 0

  1. A.70.6°
  2. B.50.2°
  3. C.39.8°
  4. D.19.4°
Show the answer and explanation

Answer: A (70.6°)

Explanation

Gradients are 3/4 and −2/3. tan θ = |(3/4 + 2/3)/(1 − ½)| = (17/12)/(1/2) = 17/6, so θ ≈ 70.6°.