Li Ye (Chinese: 李冶; Wade–Giles: Li Yeh; 1192–1279), born Li Zhi (Chinese: 李治), courtesy name Li Jingzhai (Chinese: 李敬斋), was a Chinese mathematician, politician, and writer who published and improved the tian yuan shu method for solving polynomial equations of one variable. Along with the 4th-century Chinese astronomer Yu Xi, Li Ye proposed the idea of a spherical Earth instead of a flat one before the advances of European science in the 17th century.
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Name
Li Ye was born Li Zhi, but later changed his name to Li Ye to avoid confusion with the third Tang emperor who was also named Li Zhi, removing one stroke from his original name to change the character. His name is also sometimes written as Li Chih or Li Yeh. His literary name was Renqing (Chinese: 仁卿; Wade–Giles: Jen-ch’ing) and his appellation was Jingzhai (Chinese: 敬斋; Wade–Giles: Ching-chai).
Life
Li Ye was born in Daxing (now Beijing). His father was a secretary to an officer in the Jurchen army. Li passed the civil service examination in 1230 at the age of 38, and was administrative prefect of Jun prefecture in Henan province until the Mongol invasion in 1233. He then lived in poverty in the mountainous Shanxi province. In 1248 he finished his most known work Ceyuan haijing (測圓海鏡, Sea mirror of circle measurements). Li then returned to Hebei.