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Nusret Balcı TMUA Paper 1 · Q2

Paper 1TrigonometryGeometrySequences & series

A sequence of similar sectors S1,S2,S3,…S_1,S_2,S_3,\ldots has a constant central angle θ\theta (in radians). The radius rn+1r_{n+1} of each sector is defined by the arc length sns_n of the previous sector.

Given that the sum of the perimeters of all sectors is exactly three times the perimeter of the first sector:

∑n=1∞Perimeter⁡(Sn)=3×Perimeter⁡(S1)\sum_{n=1}^\infty\operatorname{Perimeter}(S_n)=3\times\operatorname{Perimeter}(S_1)

Find the ratio of the total area of all sectors to the area of the first sector:

Ratio=∑n=1∞Area⁡(Sn)Area⁡(S1)\text{Ratio}=\frac{\sum_{n=1}^\infty\operatorname{Area}(S_n)}{\operatorname{Area}(S_1)}

Diagram for question 2

A2.62.6
B33
C1.11.1
D1.91.9
E1.81.8
F4.34.3
G2\sqrt2
H3\sqrt3

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