Ajima Naonobu

Ajima Naonobu (安島 直円, 1732 – May 20, 1798), also known as Ajima Manzō Chokuyen, was a Japanese mathematician of the Edo period.^[1]

His Dharma name was (祖眞院智算量空居士).^[2]

Ajima is credited with introducing calculus into Japanese mathematics. The significance of this innovation is diminished by a likelihood that he had access to European writings on the subject.^[3] Ajima also posed the question of inscribing three mutually tangent circles in a triangle;^[4] these circles are now known as Malfatti circles after the later work of Gian Francesco Malfatti, but two triangle centers derived from them, the Ajima–Malfatti points, are named after Ajima.^[5][6]

Ajima was an astronomer at the Shogun's Observatory (Bakufu Temmongaki).^[7]

In 1976, the International Astronomical Union (IAU) honored Ajima by identifying a crater on the Moon with his name. Naonobu is a small lunar impact crater located on the eastern Mare Fecunditatis, to the northwest of the prominent crater Langrenus.^[8][9]

In a statistical overview derived from writings by and about Ajima Naonobu, OCLC/WorldCat encompasses roughly 20+ works in 30+ publications in two languages and 40+ library holdings.^[10]

• Ajima Naonobu zenshū (安島直円全集) OCLC 017232052, collected works
• Sanpō kosō (算法考艸) OCLC 057185881, algorithms considered
• Jujireki bimmo (Introduction of the 'Works and Days Calendar')^[7]
• Anshi seiyo-reki koso (Ajima's Studies for Western Calendars)^[7]
• Ajima sensei bimmo do jutsu (Methods of Professor Ajima's 'bimmo')^[7]
• Koshoku mokyu zokkai (Introduction of Eclipses of the Sun and the Moon)^[11]
• Sansha San'en Jutsu (Methods of Three Diagonals and Three Circles)^[12]
• Fujin Isshũ (Periods of Decimal Fractions)^[1]

• Sangaku, the custom of presenting mathematical problems, carved in wood tablets, to the public in shinto shrines
• Soroban, a Japanese abacus
• Japanese mathematics

• Endō Toshisada (1896). History of mathematics in Japan (日本數學史史, Dai Nihon sūgakush). Tōkyō: _____. OCLC 122770600
• Oya, Shin'ichi. (1970). "Ajima Naonobu" in Dictionary of Scientific Biography, Vol. 1. New York: Charles Scribner's Sons. ISBN 0-684-10114-9
• Restivo, Sal P. (1992). Mathematics in Society and History: Sociological Inquiries. Dordrecht: Kluwer Academic Publishers. ISBN 978-0-7923-1765-4; OCLC 25709270
• Selin, Helaine. (1997). Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures. Dordrecht: Kluwer/Springer. ISBN 978-0-7923-4066-9; OCLC 186451909
• David Eugene Smith and Yoshio Mikami. (1914). A History of Japanese Mathematics. Chicago: Open Court Publishing. OCLC 1515528 -- note alternate online, full-text copy at archive.org