Yasuaki Aida

A Japanese mathematician in the late Edo period. His name can be read as "Yasuakira" or written as "Andan." Born in Yamagata. His childhood name was Shigematsu. At a young age, he studied mathematics under Yasuyuki Okazaki in his hometown. He learned only up to Tengen Endan (solving problems using Tengenjutsu). Later, he went to Edo, bought stocks of shogunate officials, and, calling himself Suzuki Hikosuke, worked on flood control projects in various places. He quit his job along with his colleagues, resumed his surname Aida, and tried to make a living through mathematics. He wanted to become a disciple of Sadasuke Fujita of the Seki school, who was known as the leading figure in Japanese mathematics at the time, and asked to meet Sadasuke through the connections of Sadasuke's senior disciple, Sadanori Kamiya, but they got into an argument over a trivial matter and he went back. At that time, Sadasuke Fujita's book "Seiyo Sanpo" was famous as a good book, so he targeted it and wrote "Kai Seisanpo" to attack the book. In response, the Fujita school published a book of counter-criticism, and Yasuaki published another book of criticism, and the conflict lasted for more than 20 years. During this conflict, Yasuaki's academic ability improved dramatically, and he eventually became known as the founder of the Saijo school. The name Saijo comes from his birthplace of Mogami, and also means the Saijo school. He wrote over a thousand volumes of books, of which the published works include "Tosei Jingoki," "Sanpo Kokin Tsuran," and "Sanpo Tenshoho Shinan." Of these, "Sanpo Tenshoho Shinan" was published in 1810 (Bunka 7) and is the first book to explain Tenzanjutsu in detail. It systematically solves representative formulas and can be seen as a kind of collection of formulas. After this, the Seki school also published self-study books on Tenkanjutsu, but among these, Sanpo Tenshoho Shinan was the most systematic and outstanding.

[Shinichi Oya]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

江戸後期の和算家。名は「やすあきら」とも読み、安旦と書くこともある。山形に生まれる。幼名重松。若くして郷里で岡崎安之(やすゆき)について数学を学ぶ。学んだのは天元演段（天元術を使って問題を解く）までである。のち江戸に出て幕臣の株を買い、鈴木彦助と称し、各地の治水工事に従事した。同僚とともに職を辞め、会田姓に復して、数学によって身をたてようとした。当時和算の第一人者とよばれた関流の藤田貞資(さだすけ)の門に入ろうと思い、その高弟神谷定令のつてによって貞資に面会を求めたが、ささいなことから口論になり、そのまま立ち戻った。そのころ藤田貞資の著『精要算法』が良書として有名であったので、これを標的として『改精算法』を著してこの書を攻撃した。藤田派はこれに応じて逆批判の書を出版し、安明はまた再批判の書を刊行するなど、その争いは20余年に及んだ。この争いの間に安明の学力はめきめき上達し、ついに最上(さいじょう)流開祖を名のるようになった。最上流の名はその生地最上(もがみ)から出ており、また最上(さいじょう)の流儀という意味もある。著書千数百巻、そのうち版になったのは『当世塵劫記(じんごうき)』『算法古今通覧』『算法天生法指南』などである。このうち『算法天生法指南』は1810年（文化7）の刊で、点竄(てんざん)術を詳細に説明した最初の書物である。代表的な公式を系統的に解き、一種の公式集の観がある。この後、関流でも点竄術の自習書を出したが、『算法天生法指南』はこれらのうちでもきわめて系統的で出色のものである。

［大矢真一］

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