Prove the identity:
cos2xcosx+sinx≡cosx−sinx \frac{\cos 2x}{\cos x + \sin x} \equiv \cos x - \sin x cosx+sinxcos2x≡cosx−sinx137 exam-style questions on Edexcel A Level Maths Trigonometry and Modelling, 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. Each one has a worked solution and a mark scheme showing where the marks go.