Albert Girard

Albert Girard was a French-born mathematician who lived from 1595 to 1632. He studied at the University of Leiden and made many important contributions to mathematics. Girard had early thoughts on the fundamental theorem of algebra and gave the inductive definition for the Fibonacci numbers. He was also the first person to use the abbreviations 'sin', 'cos', and 'tan' for the trigonometric functions.

Girard was the first to state in 1625 that each prime of the form 1 mod 4 is the sum of two squares. According to Charles Hutton, Girard was the first person who understood the general doctrine of the formation of the coefficients of the powers from the sum of the roots and their products. This work later helped in the development of group theory by mathematicians like Cauchy and Galois.

In addition to his work in algebra, Girard also showed how the area of a spherical triangle depends on its interior angles. This result is known as Girard's theorem. He was also a lutenist and mentioned writing a treatise on music, although it was never published.