Li Ye

Li Ye

 literary name Jingzhai

(born 1192, Luangcheng, Hebei province, China—died 1279, Yuanshi) Chinese mathematician and scholar-official who contributed to the solution of polynomial equations in one variable. When the Mongols invaded his home district in 1233, Li wandered homeless in Shanxi, Shandong, and Henan provinces. During this period he composed his main work, Ceyuan haijing (1248; “Sea Mirror of Circle Measurements”), which contains 170 problems based on one geometric diagram of a circular city wall circumscribed by a right-angled triangle. Although the problems are highly contrived, they enabled Li to list some 692 algebraic formulas for triangular areas and segment lengths. In 1264 Li was appointed to the Hanlin Academy by Kublai Khan. Li strongly criticized the political and intellectual climate of his time, though, and soon used ill health as a pretext to retire and live as a hermit.