A mechanical engineer models the efficiency, EEE, of a specialized turbine using the function
E(θ)=4cos2θ+2cosθ+6E(\theta) = 4 \cos 2\theta + 2 \cos \theta + 6E(θ)=4cos2θ+2cosθ+6
where θ \theta\,θ is the blade pitch angle in degrees.
Find all values of θ\thetaθ, for 0≤θ<360∘0 \le \theta < 360^\circ0≤θ<360∘, for which the efficiency is exactly 5. Give your solutions to one decimal place where appropriate.
(Solutions based entirely on graphical or numerical methods are not acceptable.)
Practise Edexcel A Level Maths 7.2 Double Angle Formulae with exam-style questions for A Level Maths. 24 questions, 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.