Use the identity cos2θ+sin2θ=1\cos^2\theta + \sin^2\theta = 1cos2θ+sin2θ=1 to prove that sec2θ=1+tan2θ\operatorname{sec}^2\theta = 1 + \tan^2\thetasec2θ=1+tan2θ
274 exam-style questions on Edexcel A Level Maths Trigonometric Functions, covering 6.1 Secant, Cosecant and Cotangent, 6.2 Graphs of Sec x, Cosec x and Cot x, 6.3 Using Sec x, Cosec x and Cot x, 6.4 Trigonometric Identities, and 6.5 Inverse Trigonometric Functions. Each one has a worked solution and a mark scheme showing where the marks go.