Qin Jiushao
Qin Jiushao (秦九韶; ca. 1202–1261), courtesy name Daogu, was a Song dynasty scholar who excelled as a mathematician, meteorologist, inventor, politician, and writer. Born in Ziyang, Sichuan, his family came from Shandong, and he is regarded as one of China’s greatest mathematicians, even though he did not devote himself only to math. He wrote the Mathematical Treatise in Nine Sections (1247), covering indeterminate equations, solving certain high‑degree polynomial equations, and topics on surveying and military matters. The work includes an early general form of the Chinese remainder theorem using Da yan shu algorithms. In geometry, he developed a method for finding the area of a triangle from three side lengths, a result linked to Heron’s formula. He advanced meteorology by creating rain gauges called Tianchi basins to collect weather data, and his treatise records their use in the 13th century. It also mentions large bamboo snow gauges and explains how calendar experts calculated astronomical data around the winter solstice. He introduced the zero symbol into written Chinese mathematics and described a way to evaluate polynomials by nested sums, a method now known as Horner’s method. After his mathematical work, he pursued politics, where he was ambitious and faced accusations of bribery and poisoning enemies, losing posts but still becoming wealthy.
This page was last edited on 2 February 2026, at 18:29 (CET).