Kazuyuki Sawaguchi

Japanese: 沢口一之 - さわぐち・かずゆき

Year of birth: Year of birth and death unknown. A Japanese mathematician in the early Edo period. He lived in Kyoto and studied under Hashimoto Masakazu. The legend that he studied under Seki Takakazu is doubtful. He learned Tengenshu (a method of solving equations by moving calculating sticks) from the Chinese book Sangaku Keimeng, and compiled the results in Kokin Sanpo-ki (1671). This is a compilation of the mathematical knowledge of the time, but there is almost no explanation of the essential Tengenshu. Seki Takakazu's Hatsubi Sanpo (1674) provided the answers to the 15 problems (called yudai) posed in this book. Sawaguchi was also the first to use the term "enri," which would later become important in the world of Japanese mathematician, but it had no meaning beyond the calculation of a circle. <References> The History of Mathematics in Japan Before the Meiji Period, Vol. 1, edited by the Japan Academy

(Kenichi Sato)

Source: Asahi Japanese Historical Biography: Asahi Shimbun Publications Inc. About Asahi Japanese Historical Biography

Japanese:

生年：生没年不詳
江戸初期の和算家。京都に住み,橋本正数に師事する。関孝和に師事したという伝は疑わしい。中国の『算学啓蒙』から天元術(算木の運算による方程式の解法)を学び,成果を『古今算法記』(1671)にまとめる。これは当時の数学知識を集大成しているが,肝心の天元術の解説はほとんど書かれていない。本書が提出した15個の問題(遺題という)に答えを与えたのが関孝和の『発微算法』(1674)である。のちの和算界において重要な術語である「円理」の初出も沢口によるが,円の計算以上の意味はなかった。<参考文献>日本学士院編『明治前日本数学史』1巻

(佐藤賢一)

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