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...

Ghiyāth al-Dīn Jamshīd ibn Masʾūd al-Kāshī (or Jamshīd Kāshānī) (c. 1380 Kashan, Iran – 22 June 1429 Samarkand, Transoxania) was a Persian astronomer and mathematician. In French, the Law of cosines is named Théorème d'Al-Kashi, after...