It is given that sec4x−tan4x≡1+2tan2x\sec^4x - \tan^4x \equiv 1 + 2 \tan^2xsec4x−tan4x≡1+2tan2x.
Hence solve, for −180≤x≤180-180 \leq x \leq 180−180≤x≤180, the equation,
sec4x−tan4x=3 \sec^4x - \tan^4x = 3 sec4x−tan4x=3274 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.