Show that
cos3x≡4cos3x−3cosx\cos 3x \equiv 4\cos^3 x - 3\cos xcos3x≡4cos3x−3cosx
Hence find, using algebraic integration,
∫0π6cos3x dx\int_{0}^{\frac{\pi}{6}} \cos^3 x \, dx∫06πcos3xdx
Practise Edexcel A Level Maths 11.3 Using Trigonometric Identities with exam-style questions for A Level Maths. 32 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.