When this mathematician published his version of the  Elements, it replaced Euclid's as the standard textbook. In it,  he presented the first proof that (2 i s irrational. He 
When this mathematician published his version of the  Elements, it replaced Euclid's as the standard textbook. In it,  he presented the first proof that (2 i s irrational. He also  published in 1783 the first comprehensive account of the method  of least squares. FTP, name this man who is most famous for his  simplifications of elliptic integrals.
When this mathematician published his version of the  Elements, it replaced Euclid's as the standard textbook.
Adrien-Marie Legendre