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Zhu Shijie
Yuan mathematician and itinerant teacher whose Jade Mirror of the Four Unknowns (1303) solved systems of polynomial equations in up to four unknowns
In a calculation room, a wide table holds a board of black and yellow counting rods laid in neat bundles, beside an abacus, a ruler and a sheet with a circle divided into equal parts; one person sits at a far desk with their back turned, and terraced fields lie outside.
Also known as Zi Hanqing · Hao Songting
Zhu Shijie, courtesy name Hanqing and styled Songting, came from the Yanshan region around present-day Beijing; what is known of him comes from prefaces to his books. Mo Ruo's preface to the Jade Mirror of the Four Unknowns says he traveled as a mathematics teacher for more than twenty years, drawing students wherever he went, and later settled around Yangzhou. In 1299 he published the Introduction to Mathematical Studies (Suanxue qimeng), a graded textbook running from multiplication and division to root extraction and the 'celestial element' method of setting up equations. In 1303 he published the Jade Mirror of the Four Unknowns (Siyuan yujian), which sets up and eliminates systems of higher-degree equations in as many as four unknowns and also treats sums of higher-order arithmetic series and finite-difference interpolation. The Introduction later reached Korea, where the Joseon court used it as a text for mathematics examinations, and it was reprinted in Japan.
Life and times
Dates Dates unknown; works printed in 1299 and 1303