Hong Jeong-ha

Hong Jeong-ha was a Korean mathematician of the Joseon period, born in 1684, whose date of death is unknown. His book Guiljip contained the most advanced results of its time on setting up and solving equations, and he has been called the greatest mathematician of Joseon. He belonged to the Namyang Hong clan, whose line dominated the work of government accountants of the chungin class, chosen by a special mathematics examination: of 110 clan members who passed it, 100 came from his line. Only he and two related men, Gyeong Seon-jing and Yi Sang-hyeok, wrote books on mathematics out of 1,626 recorded examination graduates. He passed the examination in 1706, became an instructor in 1718 and a professor in 1720. In 1713 he and Yu Su-seok met the Qing mathematician He Guozhu, who later checked calculations for the compendium Lüli yuanyuan, and Hong easily solved the problems set by him using the celestial element method.