Edexcel C34 2016 January — Question 10

Exam BoardEdexcel
ModuleC34 (Core Mathematics 3 & 4)
Year2016
SessionJanuary
TopicHarmonic Form

10. (a) Express \(3 \sin 2 x + 5 \cos 2 x\) in the form \(R \sin ( 2 x + \alpha )\), where \(R > 0\) and \(0 < \alpha < \frac { \pi } { 2 }\) Give the exact value of \(R\) and give the value of \(\alpha\) to 3 significant figures.
(b) Solve, for \(0 < x < \pi\), $$3 \sin 2 x + 5 \cos 2 x = 4$$ (Solutions based entirely on graphical or numerical methods are not acceptable.) $$g ( x ) = 4 ( 3 \sin 2 x + 5 \cos 2 x ) ^ { 2 } + 3$$ (c) Using your answer to part (a) and showing your working,
  1. find the greatest value of \(\mathrm { g } ( x )\),
  2. find the least value of \(\mathrm { g } ( x )\).