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Trigonometry and Modelling

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Question 16
(a).

Show that

cos⁡2x≡cos⁡2x−sin⁡2x \cos 2x \equiv \cos^2 x - \sin^2 x cos2x≡cos2x−sin2x
[1]
(b).

Hence prove the identity:

cos⁡2xcos⁡x+sin⁡x≡cos⁡x−sin⁡x \frac{\cos 2x}{\cos x + \sin x} \equiv \cos x - \sin x cosx+sinxcos2x​≡cosx−sinx
[2]
Markscheme

Trigonometry and Modelling Questions

  1. A Level
  2. /Maths
  3. /Trigonometry and Modelling

348 exam-style questions on Edexcel A Level Maths Trigonometry and Modelling, covering 7.1 Addition Formulae, 7.2 Double Angle Formulae, 7.3 Solving Trigonometric Equations, 7.4 Simplifying a cos x +- b sin x, 7.5 Proving Trigonometric Identities, and 7.6 Modelling with Trigonometric Functions. Each one has a worked solution and a mark scheme showing where the marks go.

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