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 (MEI) A Level Maths 1.7 Trigonometry, covering 1.7.1 Solve right-angled triangles, 1.7.2 Definitions of sin, cos and tan for any angle, 1.7.3 Graphs of sin, cos and tan, 1.7.4 Exact values of trig functions (degrees), 1.7.5 Area of a triangle, 1.7.6 Sine and cosine rules, 1.7.7 Identity tan = sin/cos, 1.7.8 Identity sin^2 + cos^2 = 1, 1.7.9 Solve simple trigonometric equations, 1.7.10 Exact values of trig functions (radians) (A-level only), 1.7.11 Inverse trigonometric functions (A-level only), 1.7.12 Radians and degree conversion (A-level only), 1.7.13 Arc length and area of a sector (A-level only), 1.7.14 Small angle approximations (A-level only), 1.7.15 Sec, cosec and cot functions (A-level only), 1.7.16 Graphs of reciprocal trig functions (A-level only), 1.7.17 Pythagorean identities for sec and cosec (A-level only), 1.7.18 Compound angle formulae (A-level only), 1.7.19 Double angle identities (A-level only), 1.7.20 Expressions for a cos θ ± b sin θ (A-level only), 1.7.21 Use identities to solve equations (A-level only), 1.7.22 Proofs involving trigonometric functions (A-level only), 1.7.23 Trig to solve problems in context (A-level only), and 1.7 Trigonometry. Each one has a worked solution and a mark scheme showing where the marks go.