3.5 Sum to Infinity
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A geometric sequence has first term 1 and common ratio 0.75.

a.

(i) Find the sum to infinity, S∞S_{\infty}S∞​, of the sequence.

(ii) Hence, or otherwise, evaluate ∑n=1∞(cos⁡30∘)2n\sum_{n=1}^{\infty} (\cos 30^{\circ})^{2n}∑n=1∞​(cos30∘)2n

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b.

Find the smallest positive exact value of θ\thetaθ, in radians, which satisfies the equation ∑n=0∞(2cos⁡θ)n=22−2\sum_{n=0}^{\infty} (\sqrt{2}\cos \theta)^n = \frac{2}{2 - \sqrt{2}}∑n=0∞​(2​cosθ)n=2−2​2​

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3.5 Sum to Infinity Questions

Practise Edexcel A Level Maths 3.5 Sum to Infinity with exam-style questions for A Level Maths. 18 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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3.5 Sum to Infinity Questions

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