Hiroshi Hasegawa

Japanese: 長谷川寛 - はせがわ・ひろし

Year of death: Tempo 9.11.20 (1839.1.5)
Year of birth: Tenmei 2 (1782)
A Japanese mathematician in the late Edo period. He studied under Kusaka Makoto. He excelled at educating his students, and gained many disciples, forming the "Hasegawa School" which was independent of the Seki school. He named his school "Hasegawa Dojo" and it flourished until the early Meiji period. Hiroshi showed originality not only in education but also in mathematics itself. His "Kyokukeijutsu" method, which involves transforming complex figures into simpler ones and then searching for general relationships between them, is mathematically incomplete and the method of argument is forceful, but it is highly esteemed for being a completely new idea that did not rely on conventional knowledge. Chiba Tanehide's "Sanpo Shinsho" (1830) and "Sanpo Chiho Taisei" (1837), which were widely used as textbooks until the early Meiji period, were books written by Hasegawa and published under the names of his students. After his death, his student and adopted son Hiroshi took over the dojo. Another notable student was Sato Kaiki from Echigo (Niigata Prefecture). <References> The History of Mathematics in Japan before the Meiji Period, Vol. 5, edited by the Japan Academy; Great Mathematicians of the Late Tokugawa Period, edited by Yoshimasa Michiwaki

(Kenichi Sato)

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

Japanese:

没年：天保9.11.20(1839.1.5)
生年：天明2(1782)
江戸後期の和算家。日下誠に師事。子弟の教育に優れ,多くの門弟を得て関流のなかにありながら独立した「長谷川派」を形成した。その塾を「長谷川道場」と名付けて,明治初期まで盛況を誇った。寛は教育だけでなく数学自体にも独創性を発揮した。複雑な図形を簡単な図形に変形してからその一般的な関係式を探る「極形術」は数学的には不完全で議論の方法が強引だが,在来の知識に頼らずに全く新しい発想であった点が十分評価できよう。明治初期まで教科書として広く用いられた千葉胤秀『算法新書』(1830)や『算法地方大成』(1837)は,弟子の名前で出した長谷川の著書である。没後,弟子で養子でもあった弘が道場を継いだ。他に著名な弟子に越後(新潟県)の佐藤解記がいる。<参考文献>日本学士院編『明治前日本数学史』5巻,道脇義正編『幕末の偉大なる数学者』

(佐藤賢一)

出典　朝日日本歴史人物事典：（株）朝日新聞出版朝日日本歴史人物事典について　情報

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