Albert Girard

From Wikipedia, the free encyclopedia

Albert Girard (1595–1632) was a French-born mathematician. He studied at the University of Leiden. According to the MacTutor Archive, "he had early thoughts on the fundamental theorem of algebra" and gave the inductive definition for the Fibonacci numbers. He was the first to use the Trigonometry abbreviations 'sin', 'cos' and 'tan' in a treatise. According to Ivan M. Niven, Herbert Zuckerman and Hugh Montgomery, Girard was the first to state, in 1632, that each prime of form 1mod4 was the sum of two squares in exactly one way. (See Fermat's theorem on sums of two squares.)

Girard began as a lute player, not a mathematician.

[edit] External link

• O'Connor, John J., and Edmund F. Robertson. "Albert Girard". MacTutor History of Mathematics archive.

[edit] Reference

An Introduction to the Theory of Numbers, Fifth Edition. Ivan Niven, Herbert S. Zuckerman, and Hugh L. Montgomery 1991