A mathematician is verifying a table of trigonometric identities for the variable α\alphaα.
Using the compound angle identity for sin(A+B)\sin(A + B)sin(A+B), derive the identity for sin2α \sin 2\alpha\,sin2α in terms of sinα \sin \alpha\,sinα and cosα\cos \alphacosα.
Using the compound angle identity for cos(A+B)\cos(A + B)cos(A+B), derive the identity for cos2α \cos 2\alpha\,cos2α in terms of sinα \sin \alpha\,sinα and cosα\cos \alphacosα.
Hence, write cos2α \cos 2\alpha\,cos2α as an expression containing only the term cosα\cos \alphacosα.
Hence, write cos2α \cos 2\alpha\,cos2α as an expression containing only the term sinα\sin \alphasinα.
Utilize the addition formula for tan(A+B)\tan(A + B)tan(A+B) to find an expression for tan2α \tan 2\alpha\,tan2α in terms of tanα\tan \alphatanα.
317 exam-style questions on OCR A Level Maths 1.5 Trigonometry, covering 1.5.1 Definitions for all arguments, 1.5.2 Sine and cosine rules, 1.5.3 Area of a triangle, 1.5.4 Radian measure (A-level only), 1.5.5 Small angle approximations (A-level only), 1.5.6 Graphs of basic trigonometric functions, 1.5.7 Exact values in radians (A-level only), 1.5.8 Reciprocal and inverse trigonometric ratios (A-level only), 1.5.9 Graphs of reciprocal and inverse functions (A-level only), 1.5.10 Trigonometric identities, 1.5.11 Further trigonometric identities (A-level only), 1.5.12 Double angle and compound angle formulae (A-level only), 1.5.13 Geometrical proofs of formulae (A-level only), 1.5.14 Harmonic form Rcos / Rsin (A-level only), 1.5.15 Trigonometric equations, 1.5.16 Proof involving trigonometric functions (A-level only), and 1.5.17 Trigonometric functions in context. Each one has a worked solution and a mark scheme showing where the marks go.