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A-LevelMathematicsTrigonometry9709/33 · May/June 2017 · Q13 Marks

Prove the identity cot x - tan x / cot x + tan x = cos 2x.

  1. (a)Prove the identity cot x - tan x / cot x + tan x = cos 2x.[3]

Mark scheme

Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.

  1. [B1] Express the LHS in terms of either cos x and sin x or in terms of tan x
  2. [M1] Use Pythagoras
  3. [A1] Obtain the given answer

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About this question

Topic
Trigonometry, A-Level Mathematics (syllabus 9709). Structured question, 3 marks.
Source
A-Level Mathematics, May/June 2017 Paper 3 Variant 3, question 1.

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