Given that k k\,k is a constant, prove the identity:
2sinxkcosx−secx≡2sin2xkcos2x+k−2 \frac{2 \sin x}{k \cos x - \sec x} \equiv \frac{2\sin 2x}{k\cos 2x+k-2} kcosx−secx2sinx≡kcos2x+k−22sin2x348 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.