7.2 Double Angle Formulae
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a.

By writing cos⁡3ϕ \cos 3\phi\,cos3ϕ as cos⁡(2ϕ+ϕ)\cos(2\phi + \phi)cos(2ϕ+ϕ), show that cos⁡3ϕ=4cos⁡3ϕ−3cos⁡ϕ\cos 3\phi = 4\cos^3 \phi - 3\cos \phicos3ϕ=4cos3ϕ−3cosϕ.

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b.

Solve, for 0≤ϕ≤1800 \leq \phi \leq 1800≤ϕ≤180, the equation,

12cos⁡3ϕ−9cos⁡ϕ=1.5 12\cos^3 \phi - 9\cos \phi = 1.5 12cos3ϕ−9cosϕ=1.5

Give your answers to 1 decimal place where necessary.

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7.2 Double Angle Formulae Questions

Practise Edexcel A Level Maths 7.2 Double Angle Formulae with exam-style questions for A Level Maths. 24 questions, matched to the Edexcel A Level Maths (9MA0) 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.

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7.2 Double Angle Formulae Questions

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