Qin Jiushao

Dates of birth and death unknown. A mathematician active in the late Song Dynasty in 13th century China. A native of Sichuan, his courtesy name was Daogu. Well versed in many subjects, he became an official in Jiankang Prefecture (present-day Nanjing) around 1240. In his later years, he became the governor of Meizhou (Canton), where he died. His works include the 18-volume "Sushu Nine Chapters." According to his own preface, it was completed in September 1247 (the 7th year of the Jun'yu era), and following the example of "Nine Chapters Mathematics," the entire work is divided into nine categories: Daien, Tianji, Rice Fields, Forecasting, Duties, Grains for Festivals, Camping, Military Travel, and City Goods. The first two categories deal with mathematical problems related to the calendar, and the remaining seven deal with mathematical problems necessary for politics, military affairs, markets, etc. What is noteworthy is that it contains a type of indeterminate equation called Daien Kyuichijutsu, which in Japanese mathematics is called Senkanjutsu.

[Shinichi Oya]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

生没年不詳。13世紀中国、宋(そう)代末に活躍した数学者。四川(しせん)の人。字(あざな)は道古。諸学に通じ、1240年ごろ建康府（現在の南京(ナンキン)）で役人となった。晩年は梅州（広東(カントン)）の知事となり、そこで死去した。著書に『数書九章』18巻がある。自序によれば1247年（淳祐7）9月に完成したもので、『九章算術』に倣って、全編を大衍(だいえん)類、天時類、田域類、測望類、賦役類、祭穀類、営建類、軍旅類、市物類の9類に分けている。初めの2類は暦法に、他の7類は政治・軍事・市場などに必要な数学的問題を扱っている。注目されるのは大衍求一術とよばれる不定方程式の一種が載っていることで、日本の和算で翦管術(せんかんじゅつ)とよばれるものである。

［大矢真一］

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