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Zhao Shuang
Commentator on the Zhoubi suanjing whose 'string diagram' gave a cut-and-rearrange proof of the Pythagorean relation
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 Junqing
Zhao Shuang, courtesy name Junqing (some sources give his name as Ying), left no record of his life or home; because his notes cite the Qianxiang calendar drawn up by Liu Hong at the end of the Eastern Han, scholars place him in the late Han or Three Kingdoms period, probably in the state of Wu. He annotated the Zhoubi suanjing, the oldest surviving Chinese text on astronomy and mathematics, adding an essay of about five hundred characters on the diagram of right triangles, circles and squares. Using a 'string diagram' made of four right triangles around a small central square, he proved the relation between the legs and hypotenuse by rearranging areas and derived more than twenty related formulas. His commentary survives with the Zhoubi itself and was kept when Li Chunfeng's team edited the Ten Mathematical Classics in the Tang.
Life and times
Dates Dates unknown; Three Kingdoms period