Zu Gengzhi

Zu Gengzhi

 also known as Zu Xuan

(born c. 480, Jiankang, China—died c. 525, China) Chinese government official, mathematician, astronomer, and son of Zu Chongzhi. Beginning in 504, he actively advocated his father's Daming calendar and finally succeeded in getting it officially adopted in 510. His astronomical observations with gnomons allowed him to measure the angular distance between Polaris and the celestial north pole. A mathematical fragment of his was appended by Li Chunfeng to the commentary on Jiuzhang suanshu (Nine Chapters on the Mathematical Procedures), a Chinese classic probably compiled in the 1st century AD. Fragments of his writings are also found in the astronomical chapter of Suishu (“History of the Sui Dynasty”). His fame as a mathematician rests primarily on his derivation and proof of the formula for the volume of a sphere.