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WMA11/01 Jan 2023, Question 2: Perpendicular Lines

Pearson Edexcel International AS Level Mathematics · Pure Mathematics 1 (WMA11) · Calculator · 5 marks

The question, in short

Given points P(−3, 7), Q(9, 11) and R(12, 2), show angle PQR is 90°, then use the rectangle PQRS to find S's coordinates.

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

Part (a) · 3 marks

Show that angle PQR equals 90° using the coordinates of P, Q and R.

  1. 1Gradient PQ = (11 − 7)/(9 + 3) = 4/12 = 1/3
  2. 2Gradient QR = (11 − 2)/(9 − 12) = 9/(−3) = −3
  3. 3(1/3) × (−3) = −1, so PQ is perpendicular to QR and angle PQR = 90°

AnswerShown: gradient PQ = 1/3, gradient QR = −3, and (1/3) × (−3) = −1, so angle PQR = 90°

Part (b) · 2 marks

Given PQRS is a rectangle, work out the coordinates of point S.

  1. 1Vector QR = (12 − 9, 2 − 11) = (3, −9)
  2. 2PS = QR, so S = (−3 + 3, 7 − 9) = (0, −2)

AnswerS(0, −2)

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