Mathematician:Albert Girard

Professional French lutenist who also studied mathematics, working in the fields of algebra, trigonometry and arithmetic.

Gave an inductive formula for the Fibonacci numbers.

First stated in 1632 that every prime of the form $4 k + 1$ is the sum of two squares in only one way.

Invented the symbol $$\sqrt[n]x$$ for the $n$th root of $$x$$.

His work led eventually to the creation of group theory.

See the page on Albert Girard at MacTutor Archive by J J O'Connor and E F Robertson.

Nationality
French

History

 * Born: 1595 in St Mihiel, France.
 * Died: 8 Dec 1632 in Leiden, Netherlands.

Theorems

 * Girard's Theorem

Books and Papers
(titles unknown)
 * A translation of the works of Stevin (1625)
 * A treatise on trigonometry (1626)


 * "Invention Nouvelle en l'Algèbre" (1629)