Zhào Jūnqīng 趙君卿 (personal name Shuǎng 爽; zì Jūnqīng — preferred form) — late-Hàn / Wèi-Jìn-period mathematician-and-astronomer, the principal commentator on the Zhōubì suànjīng 周髀算經 (KR3f0001) — the foundational Chinese mathematical-astronomical treatise. The Suí jīngjí zhì and the Táng yìwén zhì attribute the commentary to “Zhào Yīng” 趙嬰; the Sòng zhì and Bào Hànzhī 鮑澣之’s 1213 edition give “Zhào Jūnqīng”; the SKQS tíyào and Sòng Chóngwén zǒngmù identify the two as the same person, with 嬰 / 爽 being graphic-corruption (爽 is the personal name, with 嬰 = scribal-error). Zhào Shuǎng’s preface to the Zhōubì invokes Zhāng Héng’s Língxiàn and other late-Hàn references — placing him after Zhāng Héng (78–139) and before Zhēn Luán’s 甄鸞 6th-century zhòngshù (re-elaboration). Zhào Shuǎng’s prefatorial diagrams of the gōugǔ (right-angle / Pythagorean) theorem with red-and-yellow-shaded squares (zhūhuáng zhī shí 朱黃之實) — establishing the bèichā jiǎnbìng (multiply-subtract-add-combine) operations on areas — produce a complete proof of the Pythagorean theorem, the earliest such proof in Chinese mathematics. The SKQS editors call Zhào “the master of mathematical learning” (誠算學之宗師也).