Abū al-Wafāʾ Muḥammad ibn Muḥammad ibn Yaḥyā ibn Ismāʿīl ibn al-ʿAbbās al-Būzjānī was a Persian mathematician and astronomer who worked in Baghdad. He made important innovations in spherical trigonometry, and his work on arithmetic for businessmen contains the first instance of using negative numbers in a medieval Islamic text. June 15, 940 – July 20, 998; died at 58. Alive at the same time as Murasaki Shikibu, Leif Erikson, Farabi, Sylvester II, and Vladimir the Great. Wiki link