Given that θ \theta\,θ is small, use the small angle approximation of cosθ \cos \theta\,cosθ to show that
5cos(θ)−cos2(2θ)≈4+1.5θ2−4θ4 5 \cos(\theta) - \cos^2(2\theta) \approx 4 + 1.5\theta^2 - 4\theta^4 5cos(θ)−cos2(2θ)≈4+1.5θ2−4θ4Hence find an approximation of 5cos(θ)−cos2(2θ)5 \cos(\theta) - \cos^2(2\theta)5cos(θ)−cos2(2θ) when θ=2∘\theta = 2^\circθ=2∘
Calculate the percentage error in your approximation
Practise Edexcel A Level Maths Radians with exam-style questions for A Level Maths. 52 questions covering 5.1 Radian Measure, 5.2 Arc Length, 5.3 Areas of Sectors and Segments, 5.4 Solving Trigonometric Equations, and 5.5 Small Angle Approximations, 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.