By writing sin3θ \sin 3\theta\,sin3θ as sin(2θ+θ)\sin (2\theta + \theta)sin(2θ+θ) show that sin3θ=3sinθ−4sin3θ\sin 3\theta = 3\sin\theta - 4\sin^3 \thetasin3θ=3sinθ−4sin3θ
Solve, for 0≤θ≤1800 \leq \theta \leq 1800≤θ≤180, the equation,
3sinθ−4sin3θ=0.4 3\sin\theta - 4\sin^3 \theta = 0.4 3sinθ−4sin3θ=0.4Give your answers to 1 decimal place.
137 exam-style questions on Edexcel A Level Maths Trigonometry and Modelling, 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. Each one has a worked solution and a mark scheme showing where the marks go.