By writing cos3θ \cos 3\theta\,cos3θ as cos(2θ+θ)\cos(2\theta + \theta)cos(2θ+θ) show that cos3θ=4cos3θ−3cosθ\cos 3\theta = 4\cos^3\theta - 3\cos\thetacos3θ=4cos3θ−3cosθ
Solve, for 0≤θ≤π0 \leq \theta \leq \pi0≤θ≤π, the equation,
4cos3θ−3cosθ=0.5 4\cos^3\theta - 3\cos\theta = 0.5 4cos3θ−3cosθ=0.5Give your answers in terms of π\piπ.
Practise Edexcel A Level Maths Trigonometry and Modelling with exam-style questions for A Level Maths. 100 questions covering 7.1 Addition Formulae, 7.2 Double Angle Formulae, 7.3 Solving Trigonometric Equations, 7.4 Simplifying a cos x +- b sin x, 7.5 Proving Trigonometric Identities, and 7.6 Modelling with Trigonometric Functions, 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.