In an investigation of harmonic motion, a physicist requires the double-angle identities for an angle θ\thetaθ.
Starting with the identity for sin(A+B)\sin(A + B)sin(A+B), find an expression for sin2θ \sin 2\theta\,sin2θ in terms of sinθ \sin \theta\,sinθ and cosθ\cos \thetacosθ.
Starting with the identity for cos(A+B)\cos(A + B)cos(A+B), find an expression for cos2θ \cos 2\theta\,cos2θ in terms of sinθ \sin \theta\,sinθ and cosθ\cos \thetacosθ.
Use the result from part (b) to express cos2θ \cos 2\theta\,cos2θ as a function of cosθ \cos \theta\,cosθ only.
Use the result from part (b) to express cos2θ \cos 2\theta\,cos2θ as a function of sinθ \sin \theta\,sinθ only.
Derive the formula for tan2θ \tan 2\theta\,tan2θ in terms of tanθ \tan \theta\,tanθ using the expansion of tan(A+B)\tan(A + B)tan(A+B).
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.