The displacement of a buoy from its equilibrium position, in decimetres, is modeled by the function
h(t)=12cost−5sinth(t) = 12\cos t - 5\sin th(t)=12cost−5sint
where ttt is the time in minutes since the start of the observation.
Express h(t)h(t)h(t) in the form Rcos(t+α)R\cos(t + \alpha)Rcos(t+α), where R>0R > 0R>0 and 0<α<π20 < \alpha < \frac{\pi}{2}0<α<2π. Give the exact value of RRR and the value of α\alphaα, in radians, to 3 decimal places.
Let the stability index of the buoy be defined by S(t)=10−3h(4t)S(t) = 10 - 3h(4t)S(t)=10−3h(4t).
Using the answer to part (a), (i) write down the exact maximum value of S(t)S(t)S(t). (ii) find the smallest positive value of ttt for which this maximum value occurs, giving your answer to 2 decimal places.
Practise Edexcel A Level Maths 7.4 Simplifying a cos x +- b sin x with exam-style questions for A Level Maths. 19 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.