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Cutting cakes and kissing circles - MaRDI portal

Cutting cakes and kissing circles (Q6169272)

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scientific article; zbMATH DE number 7710455
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Cutting cakes and kissing circles
scientific article; zbMATH DE number 7710455

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    Cutting cakes and kissing circles (English)
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    11 July 2023
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    For \(n\geq 2\), suppose there are circles \(c_1, \dots, c_n\) on the plane such that \(c_i\cap c_{i+1}\) is a point \(S_i\) for \(1\leq i\leq n\), where \(c_{n+1} = c_1\). For \(P_1\in c_1\), let the straight line \(P_1S_1\) intersect \(c_2\) at \(P_2\). Inductively, let the straight line \(P_iS_i\) intersect \(c_{i+1}\) at \(P_{i+1}\). If \(n\) is even then \(P_{n+1}=P_1\) and if \(n\) is odd then \(P_1P_{n+1}\) is a diameter of \(c_1\). The author presents a nice sketch of a proof of this. If \(n\) is odd then changing the position of \(P_1\), one gets a different diameter of \(c_1\) and hence gets the center of \(c_1\). Using two tricks by \textit{J. Steiner} [Die geometrischen Constructionen, ausgeführt mittelst der geraden Linie und eines festen Kreises. Herausgegeben von A. J. von Oettingen. Frankfurt am Main: Harri Deutsch (1895; JFM 26.0545.01)], the author presents constructions to divide a circular disc with a marked center into \(m\) pieces of equal size where \(m=2, 3, 4\) and 6. The author presents this article in terms of cutting circular cakes into equal size pieces. More precisely, if there are odd numbers of circular cakes then using the above two constructions, one can cut any one of the cakes into \(m\) pieces of equal size where \(m=2, 3, 4\) and 6.
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    circular disc
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    dividing pieces of equal size
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