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WMA11/01 Oct 2019, Question 1: Radians, Arcs and Sectors

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

The question, in short

Sector AOB has radius r cm and angle 1.25 radians; its area is 15 cm². Find the exact r, then the exact perimeter in simplest form.

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

Part (a) · 2 marks

Use the sector area formula with area 15 and angle 1.25 to find the exact value of r.

  1. 1Area = ½r²θ: ½ × r² × 1.25 = 15
  2. 2r² = 24
  3. 3r = √24 = 2√6

Answerr = 2√6 (= √24)

Part (b) · 3 marks

Using your r, find the exact perimeter of the sector, giving the answer in simplest form.

  1. 1Arc length s = rθ = 2√6 × 1.25 = 2.5√6
  2. 2Perimeter = 2r + rθ = 4√6 + 2.5√6
  3. 3= 6.5√6 = 13√6/2 cm

Answer13√6/2 cm (= 6.5√6)

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Also searched as: WMA11 October 2019 · WMA11/01 · wma11 oct19 · IAS Maths Pure Mathematics 1 October 2019 · question 1.
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