Show that, for small values of θ\thetaθ measured in radians,
3cos2θ+sin4θ−2tan3θ≈A+Bθ+Cθ2 3 \cos 2\theta + \sin 4\theta - 2 \tan 3\theta \approx A + B\theta + C\theta^2 3cos2θ+sin4θ−2tan3θ≈A+Bθ+Cθ2where AAA, BBB and CCC are constants to be found.
Use your answer to part (a) to find an approximation for
3cos0.12+sin0.24−2tan0.18 3 \cos 0.12 + \sin 0.24 - 2 \tan 0.18 3cos0.12+sin0.24−2tan0.18Give your answer to three decimal places.
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.