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A necklace of exactly six spheres can be constructed around the “neck” between spheres a and b. (© Nippon.com)
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A recreation of Irisawa’s sangaku based on the details in Kokon sankan, currently displayed at Samukawa Shrine. (Courtesy Abe Haruki)
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Digital archive of Kokon sankan, Mathematical Library, Department of Mathematics, Kyoto University.
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Methods for extracting a determinant.
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“Daseki jutsu” in Katsuyō sanpō (courtesy National Diet Library Digital Archive) beside Ars Conjectandi (courtesy Internet Archive).
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Sangi three to five inches long were arranged in the cells of a sanban to represent numbers. This image shows the digits “19376.” (Courtesy Fukagawa Hidetoshi)
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A sangaku donated to Isobe Shrine in Sabae, Fukui, posing a problem about how much sake each attendee at the flower-viewing party drinks. (Courtesy Isobe Shrine)