Xú Yǒurén 徐有壬
Style name Jūnqīng 钧卿 (also written 君青). Native of Wúxiàn 吳縣 (Sūzhōu prefecture, Jiāngsū). Born Jiāqìng 5 (1800); died Xiánfēng 10 (1860). CBDB c_personid 61310 confirms the lifedates. Jìnshì of Dàoguāng 9 (1829). Rose to become Governor of Jiāngsū 江蘇巡撫 in the late 1850s.
Combined a major official career with serious mathematical work. He died on 28 May 1860 (Xiánfēng 10/4/8) at the fall of Sūzhōu to the Tàipíng Tiānguó forces under Lǐ Xiùchéng 李秀成 — refusing to flee and committing suicide with his family when the city walls fell. He was posthumously honoured as Zhuāngmǐn 莊愍.
His mathematical work is concentrated on cyclotomic and trigonometric series (continuing the 項名達 Xiàng Míngdá / 戴煦 Dài Xù tradition; cf. KR3fc069, KR3fc073) and on the application of those series to high-precision computation of the ratio π / circumference. His Cèyuán mìlǜ 測圓密率 (KR3fc075) is the principal Chinese-language presentation of these methods of his generation. He was a correspondent of 戴煦 Dài Xù and of 李善蘭 Lǐ Shànlán; the XiāoshānSūzhōu mathematical circle of which he was a member was the principal organisational nexus of mid-nineteenth-century indigenous Chinese mathematical work.