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 ronin 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 a 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 Shuki.[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]
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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]