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0606/13 Oct/Nov 2025, Question 3: Connected Rates of Change and Small Changes

Cambridge IGCSE Additional Mathematics 0606 · Paper 13 (Non-calculator) · Non-calculator · 4 marks

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The question, in short

Given y = sin 5x on 0 ≤ x ≤ π/10, use calculus and the supplied table to estimate how much x changes when y rises from √3/2 by 0.01.

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

Solution · 4 marks

  1. 1sin 5x = √3/2 gives 5x = π/3, so x = π/15
  2. 2dy/dx = 5 cos 5x
  3. 3At x = π/15: dy/dx = 5 cos(π/3) = 5/2
  4. 4δy ≈ (dy/dx) δx, so 0.01 = (5/2) δx
  5. 5δx = 0.004

Answerδx = 0.004 or 1/250

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