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A-LevelMathematicsTrigonometry9709/21 · Oct/Nov 2020 · Q66 Marks

It is given that 3 sin 2θ = cos θ where θ is an angle such that 0° < θ < 90°.

  1. (a)Find the exact value of sin θ.[2]
  2. (b)Find the exact value of sec θ.[2]
  3. (c)Find the exact value of cos 2θ.[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

  1. [B1] Use sin 2θ= 2 sin θ cos θ
  2. [B1] Obtain sin θ = 1/6
  3. [M1] Use correct identity or identities to find value of sec θ
  4. [A1] Obtain 6/√35 or exact equivalent
  5. [M1] Use correct identity or identities to find value of cos 2θ
  6. [A1] Obtain 17/18 or exact equivalent

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About this question

Topic
Trigonometry, A-Level Mathematics (syllabus 9709). Structured question, 6 marks.
Source
A-Level Mathematics, Oct/Nov 2020 Paper 2 Variant 1, question 6.

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