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.
Practise AQA A Level Maths 1.8 E: Trigonometry with exam-style questions for A Level Maths. 239 questions covering 1.8.1 Trigonometric definitions, rules and radians, 1.8.2 Small angle approximations (A-level only), 1.8.3 Trigonometric functions and exact values, 1.8.4 Reciprocal and inverse trigonometric functions (A-level only), 1.8.5 Trigonometric identities, 1.8.6 Compound and double angle formulae (A-level only), 1.8.7 Solving trigonometric equations, 1.8.8 Proofs with trigonometric identities, and 1.8.9 Trigonometry in context, matched to the AQA A Level Maths (7357) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.