Dài Xù 戴煦
Style name Èshì 鄂士 (also Hèshù 鶴墅). Native of Qiántáng 錢塘 (modern Hángzhōu 杭州, Zhèjiāng). Born Jiāqìng 10 (1805); died Xiánfēng 10 (1860), reportedly committing suicide during the Tàipíng Tiānguó 太平天國 occupation of Hángzhōu. CBDB c_personid 91692 confirms the lifedates.
The principal Zhèjiāng mathematician of the Dàoguāng to Xiánfēng generation. Dài Xù’s mathematical career is concentrated on tabular methods — the construction of trigonometric, logarithmic, and other mathematical tables with rapid computational procedures, the jiéfǎ 捷法 (“rapid methods”) tradition. His principal work KR3fc073 Qiúbiǎo jiéshù 求表捷術 in 13 juàn is the major Chinese-language treatise of this tradition, and was one of the most influential mid-nineteenth-century mathematical works in China.
Dài Xù also served as the principal completer and editor of 項名達 Xiàng Míngdá’s posthumous works, most importantly the Xiàngshù yīyuán (KR3fc069) which he completed after Xiàng’s death in 1850 and saw through to publication. This editorial work makes Dài Xù the central conserving figure of the Zhèjiāng / Hángzhōu mathematical lineage of the second quarter of the nineteenth century.
Dài Xù’s mathematical correspondence with Xiàng Míngdá in the 1830s and 1840s is preserved in part in Xiàng’s Xiàngshù yīyuán and is a principal documentary source for the Zhèjiāng mathematical scene of the period. Dài Xù was also a correspondent of 李善蘭 Lǐ Shànlán in the 1840s; the two men together represent the indigenous Chinese mathematical work of the generation immediately preceding the mid-century reception of European symbolic algebra. The death of Dài Xù in 1860 in the Tàipíng occupation, like that of 羅士琳 Luó Shìlín in 1853 in similar circumstances, marks the end of the early-Qīng to mid-Qīng kǎozhèng mathematical project.
Dài Xù’s brother Dài Kǎi 戴凱 was also a mathematician working in the same Hángzhōu milieu.