Qin Jiushao

Qín Jiǔshào (秦九劭 in simplified Chinese, 秦九韶 in traditional characters, Ch'in Chiu-Shao in Wade-Giles transliteration) (ca. 1202 – 1261) was a mathematician, inventor and Chinese politician, considered one of the greatest mathematicians in Chinese history. He was also an expert in many other fields and held a number of administrative positions in the bureaucracies of various Chinese provinces. Qin discovered what, centuries later, would become known as Horner's algorithm. In addition, he was the inventor of the Tianchi bowls, instruments used at the time to collect meteorological information.

Qin Jiushao's reputation as a mathematician is based on the 数书九章 ("Shùshū jiŭzhāng", Mathematical Treatise in Nine Sections) edited in 1247. The treatise covered matters ranging from indeterminate analysis to military matters. In the treatise, Qin included a version of the Chinese remainder theorem, which used algorithms to solve problems.

Qin explains for the first time how Chinese experts calculated astronomical data according to the rhythm of the winter solstice. Among his achievements is the introduction of a technique for solving equations, finding sums of arithmetic series and solving linear systems. He also introduced the use of the zero symbol in Chinese mathematics.