1380-1429

Persian Mathematician and Astronomer

Al-Kashi made the first notable use of decimal fractions, and it would be two centuries before any mathematician improved on his calculation of π to 16 places. During his career, he worked with a number of prominent figures in the mathematical and scientific communities of Muslim central Asia, in particular Ulugh Beg (1393-1449) and Qadi Zada al-Rumi (1364-1436).

Known sometimes as Jamshid al-Kashi, the mathematician's full name was Ghiyath al-Din Jamshid Mas'ud al-Kashi. He was born in the desert town of Kashan, near the eastern tip of the central Iranian mountain range. During his early years, the region was terrorized by the invasions of Timur (or Tamurlane) (1336-1405), and the young al-Kashi lived in poverty. With the death of the conqueror and the accession of his son Shah Rokh, however, the life of the people in general—and of al-Kashi in particular—improved dramatically.

Al-Kashi...