Kashi, Jamshid Ibn Masud Al

Kashi, Jamshid Ibn Masud Al 

Year of birth unknown; died circa 1436–37. Mathematician and astronomer.

Al-Kashi worked from about 1420 to 1430 at the Samarkand Observatory of Ulug Beg. In his work Key of Arithmetic (1427) he set forth techniques for extracting roots based on the application of the binomial for mula to integral powers. He also introduced decimal fractions into use and described their rules of operation. Al-Kashi proposed a method for the approximate solution of third-degree equations. In his Treatise on the Circle (c. 1427) he computed a value for the number π accurate to 17 decimal places.