Given that θ \theta\,θ is small, use the small angle approximation of cosθ \cos \theta\,cosθ to show that
3cos(2θ)+cos2(θ)≈4−7θ2+0.25θ4 3 \cos(2\theta) + \cos^2(\theta) \approx 4 - 7\theta^2 + 0.25\theta^4 3cos(2θ)+cos2(θ)≈4−7θ2+0.25θ4Hence find an approximation of 3cos(2θ)+cos2(θ)3 \cos(2\theta) + \cos^2(\theta)3cos(2θ)+cos2(θ) when θ=4∘\theta = 4^\circθ=4∘
Calculate the percentage error in your approximation
Practise Edexcel A Level Maths 5.5 Small Angle Approximations with exam-style questions for A Level Maths. 25 questions, matched to the Edexcel A Level Maths (9MA0) 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.