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4024/12 Oct/Nov 2020, Question 17: Locus construction

Cambridge O Level Mathematics 4024 · Paper 12 (Non-calculator) · Non-calculator · 4 marks

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The question, in short

From a diagram of boats A, B and C, measure a bearing and carry out a construction and shading inside triangle ABC.

Summarised in our own words. Use the official paper for the exact wording and the diagram.

Part (a) · 1 mark

Measure the bearing of B from A using the diagram.

  1. 1Measure the angle clockwise from the North line at A to the line AB
  2. 2Bearing of B from A ≈ 330°

Answer328° to 332°

Part (bi) · 2 marks

With compasses and straight edge only, construct the locus inside triangle ABC equidistant from B and C.

  1. 1With compasses centred on B, draw arcs above and below BC (radius more than half of BC)
  2. 2With the same radius, centred on C, draw arcs crossing the first two
  3. 3Rule a line through the two crossing points: the perpendicular bisector of BC

AnswerAcceptable perpendicular bisector of BC with two pairs of correct arcs

Part (bii) · 1 mark

Shade the region inside triangle ABC closer to AC than BC and closer to C than B.

  1. 1Nearer to AC than BC: the side of the angle bisector CX towards A
  2. 2Nearer to C than B: the side of the perpendicular bisector towards C
  3. 3Shade the region inside the triangle on both of these sides (the bottom left region)

AnswerCorrect (bottom left) region shaded

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Also searched as: 4024/12/O/N/20 · 4024_w20_qp_12 · 4024 w20 12 · question 17.
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