Show that tan2x≡1−cos2x1+cos2x\displaystyle \tan^2 x \equiv \frac{1 - \cos 2x}{1 + \cos 2x}tan2x≡1+cos2x1−cos2x
Hence solve, for −π≤x≤π-\pi \leq x \leq \pi−π≤x≤π,
tan2x=3 \tan^2 x = 3 tan2x=3348 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.