Seki Takakazu (関 孝和, 1642 – December 5, 1708), also known as Seki Kōwa (関 孝和), was a Japanese mathematician and author of the Edo period.
Seki laid foundations for the subsequent development of Japanese mathematics known as wasan; and he has been described as "Japan's Newton".
He created a new algebraic notation system and, motivated by astronomical computations, did work on infinitesimal calculus and Diophantine equations. A contemporary of German polymath mathematician and philosopher Gottfried Leibniz and British mathematician Isaac Newton, Seki's work was independent. His successors later developed a school dominant in Japanese mathematics until the end of the Edo period.
While it is not clear how much of the achievements of wasan are Seki's, since many of them appear only in writings of his pupils, some of the results parallel or anticipate those discovered in Europe. For example, he is credited with the discovery of Bernoulli numbers. The resultant and determinant (the first in 1683, the complete version no later than 1710) are attributed to him. These achievements are astonishing, considering that Japanese mathematics before his appearance was at such a primitive stage. For example, comprehensive introduction of 13th century Chinese algebra was made as late as 1671, by Kazuyuki Sawaguchi.
- "Seki Takakazu" | 2019-06-21 | 84 Upvotes 12 Comments
Otokichi (音吉 or 乙吉), also known as Yamamoto Otokichi and later known as John Matthew Ottoson (1818 – January 1867), was a Japanese castaway originally from the area of Onoura near modern-day Mihama, on the west coast of the Chita Peninsula in Aichi Prefecture.
- "Otokichi" | 2021-01-25 | 262 Upvotes 71 Comments
Yasuke (variously rendered as 弥助 or 弥介, 彌助 or 彌介 in different sources) was a man of African origin who served as a retainer under the Japanese daimyō Oda Nobunaga. In 1579, Yasuke arrived in Japan in the service of Italian Jesuit missionary Alessandro Valignano, Visitor of Missions in the Indies, in India.
Yasuke is thought by some to have been the first African that Nobunaga had ever seen and he was one of the many Africans to have come with the Portuguese to Japan during the Nanban trade. He was also present during the Honnō-ji Incident, the forced suicide of Nobunaga at the hands of his samurai general Akechi Mitsuhide on 21 June 1582.