Arima Yoriyuki

Lord of Kurume Domain, Chikugo Province (Fukuoka Prefecture). Famous as a daimyo's mathematician. His pen name was Rinsoan and many others. He learned mathematics from Yamaji Shizumi, compiled the achievements of Seki Takakazu, Takebe Katahiro, Matsunaga Yoshisuke, and others, and wrote many books including his own ideas. Although only "Shuuki Sanpo" (1769) was published, it was very well received as a good textbook on dot-plot. At the end of the book, he showed the formulas for three infinite series (enri) related to arc length. He patronized many mathematicians, including the father and son Fujita Sadasuke and Kagen, as his vassals. The reason why the Seki school gained a higher reputation than other schools was largely due to the support of Arima Yoritsune. He was born in Kurume and died there.

[Shimohira Kazuo]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

筑後(ちくご)国（福岡県）久留米(くるめ)藩主。大名(だいみょう)の数学者として有名。号は林窓菴(りんそうあん)ほか多数。数学を山路主住(やまじぬしずみ)に習い、関孝和(せきたかかず)、建部賢弘(たけべかたひろ)、松永良弼(よしすけ)たちの業績をまとめ、しかも自分のくふうも含めて多くの著書を著す。刊行されたのは『拾璣算法(しゅうきさんぽう)』（1769）だけであるが、点竄(てんざん)のよい教科書として大いに歓迎された。巻末に、弧の長さに関する三つの無限級数（円理）の公式を示した。藤田貞資(さだすけ)・嘉言(かげん)父子のほか多くの数学者を家臣にして庇護(ひご)した。関流が他の流派より評判を高くしたのは有馬頼徸の援助によるところが大きい。久留米に生まれ、同地で没。

［下平和夫］

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