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1.8 E: Trigonometry

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Question 31
a.

Given that θ \theta\,θ is small, use the small angle approximation of cos⁡θ \cos \theta\,cosθ to show that

4cos⁡(θ)+cos⁡2(2θ)≈5−6θ2+4θ4 4 \cos(\theta) + \cos^2(2\theta) \approx 5 - 6\theta^2 + 4\theta^4 4cos(θ)+cos2(2θ)≈5−6θ2+4θ4
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b.

Hence find an approximation of 4cos⁡(θ)+cos⁡2(2θ)4 \cos(\theta) + \cos^2(2\theta)4cos(θ)+cos2(2θ) when θ=3∘\theta = 3^\circθ=3∘

[2]
c.

Calculate the percentage error in your approximation

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Markscheme

1.8 E: Trigonometry Questions

  1. A Level
  2. /Maths
  3. /1.8 E: Trigonometry

317 exam-style questions on AQA A Level Maths 1.8 E: Trigonometry, covering 1.8.1 Trigonometric definitions, rules and radians, 1.8.2 Small angle approximations (A-level only), 1.8.3 Trigonometric functions and exact values, 1.8.4 Reciprocal and inverse trigonometric functions (A-level only), 1.8.5 Trigonometric identities, 1.8.6 Compound and double angle formulae (A-level only), 1.8.7 Solving trigonometric equations, 1.8.8 Proofs with trigonometric identities, and 1.8.9 Trigonometry in context. Each one has a worked solution and a mark scheme showing where the marks go.

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