Given that θ \theta\,θ is small, use the small angle approximation of cosθ \cos \theta\,cosθ to show that
2cos(3θ)+cos2(θ)≈3−10θ2+0.25θ4 2 \cos(3\theta) + \cos^2(\theta) \approx 3 - 10\theta^2 + 0.25\theta^4 2cos(3θ)+cos2(θ)≈3−10θ2+0.25θ4Hence find an approximation of 2cos(3θ)+cos2(θ)2 \cos(3\theta) + \cos^2(\theta)2cos(3θ)+cos2(θ) when θ=6∘\theta = 6^\circθ=6∘
Calculate the percentage error in your approximation
Practise AQA A Level Maths 1.8 E: Trigonometry with exam-style questions for A Level Maths. 239 questions 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, matched to the AQA A Level Maths (7357) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.