Ajima Naonobu
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Ajima Naonobu
Ajima Naonobu
DiedMay 20, 1798
Known forCredited with introducing calculus into Japanese mathematics

Ajima Naonobu ( , 1732 - May 20, 1798), also known as Ajima Manz? Chokuyen, was a Japanese mathematician of the Edo period.[1]

His Dharma name was ().[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]

Selected works

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 zensh? () OCLC 017232052, collected works
  • Sanp? kos? (?) 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 Issh? (Periods of Decimal Fractions)[1]

See also


  1. ^ a b Smith, David. (1914). A History of Japanese Mathematics, pp. 195-205., p. 195, at Google Books
  2. ^ "". ? (in Japanese). Retrieved .
  3. ^ Restivo, Sal P. (1992). Mathematics in Society and History: Sociological Inquiries, p. 58. , p. 58, at Google Books
  4. ^ Fukagawa, Hidetoshi; Rothman, Tony (2008), Sacred mathematics: Japanese temple geometry, Princeton University Press, p. 79, ISBN 978-0-691-12745-3.
  5. ^ Weisstein, Eric W. "Ajima-Malfatti Points". MathWorld..
  6. ^ C. Kimberling, Encyclopedia of Triangle Centers Archived 2012-04-19 at the Wayback Machine, X(179) and X(180).
  7. ^ a b c d Jochi, Shigeru. (1997). "Ajima Naonobu," Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures, p. 38., p. 38, at Google Books
  8. ^ United States Geological Survey: Naonobu Gazetteer of Planetary Nomenclature, International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN)
  9. ^ "Naonobu lunar crater (in Japanese)". Archived from the original on 2007-12-21. Retrieved .
  10. ^ WorldCat Identities Archived 2010-12-30 at the Wayback Machine: ? 1739-1798
  11. ^ Jochi, pp. 38-39., p. 38, at Google Books
  12. ^ Jochi, p. 39., p. 39, at Google Books


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