Use the identity cos2θ+sin2θ=1\cos^2 \theta + \sin^2 \theta = 1cos2θ+sin2θ=1 to prove that tan2θ=sec2θ−1\tan^2 \theta = \sec^2 \theta - 1tan2θ=sec2θ−1.
Solve, for 0≤θ<360∘0 \leq \theta < 360^\circ0≤θ<360∘, the equation
2tan2θ+4secθ+sec2θ=2. 2 \tan^2 \theta + 4 \sec \theta + \sec^2 \theta = 2. 2tan2θ+4secθ+sec2θ=2.4 exam-style questions on Edexcel A Level Old Maths Trigonometry. Each one has a worked solution and a mark scheme showing where the marks go.