By writing sin3A \sin 3A\,sin3A as sin(2A+A)\sin(2A + A)sin(2A+A), show that sin3A=3sinA−4sin3A\sin 3A = 3\sin A - 4\sin^3 Asin3A=3sinA−4sin3A.
Solve, for 0≤A≤1800 \leq A \leq 1800≤A≤180, the equation,
3sinA−4sin3A=0.85 3\sin A - 4\sin^3 A = 0.85 3sinA−4sin3A=0.85Give your answers to 1 decimal place.
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.