Sakabe Kōhan

In this Japanese name, the surname is Sakabe.

Sakabe Kōhan (坂部 廣胖; 1759 – September 16, 1824) was a Japanese mathematician in the Edo period.^[1]

Sakabe served for a time in the Fire Department of the shogunate, but he resigned that position to become a rōnin or masterless samurai. He spent the rest of this life in study, in teaching, and in promoting mathematics education in Japan.^[2]

Sakabe was a student of Ajima Naonobu.^[3][4]

Sakabe investigated some European and Chinese works which had appeared in Japan, but his general method was later construed to be innovative, clarified and thus improved.^[5] Foreign influence shows itself indirectly some of his published work.^[6]

Sakabe's Sampo Tenzan Shinan-roku (Treatise on Tenzan Algebra) in 1810 was the first published work in Japan proposing the use of logarithmic tables. He explained that "these tables save much labor, [but] they are but little known for the reason that they have never been printed in our country."^[7] Sakabe's proposal would not be realized until twenty years after his death when the first extensive logarithmic table was published in 1844 by Koide Shuke.^[8]

In Sakabe's Treatise on Tenzan Algebra, mathematical problems are arranged in order from easy problems to difficult ones. The text presents a method for finding the length of a circumference and the length an arc of an ellipse. This was the first appearance of the problems pertaining to ellipses in printed books in Japan.^[9]

Selected works

In a statistical overview derived from writings by and about Harry Smith Parkes, OCLC/WorldCat encompasses roughly 10+ works in 10+ publications in 1 language and 10+ library holdings.^[10]

This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by adding missing items with reliable sources.

• 1795 — Shinsen Tetsujutsu^[2]
• 1802 — Kaiujutsu-keima (Considerations on the theory of the polygon)^[2]
• 1803 — Rippō-eijiku, method for finding cube root^[4]
• 1810 — Tenzan Shinan-roku (點竄指南錄) OCLC 22057236896, Treatise on Tenzan Algebra^[7]
• 1812 — Kwanki-kodo-shōhō, measurement of spherical arcs and trigonometrical tables^[11]
• 1816 — Kairo Anshin-roku (海路安心錄) OCLC 122810576, theory of navigation applying the spherical astronomy of the West^[6]

See also

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