1865-1963

French mathematician who founded the branch of mathematics known as functional analysis, and developed a formula for determining the number of prime numbers. The ancient Greeks had already proved that for every prime number there is a larger one. Using his work on the Riemann zeta function, Hadamard was able to demonstrate that the number of prime numbers less than x is asymptotically equal to x/log x. He made many other fundamental contributions to mathematics and published a book entitled The Psychology of Invention in the Mathematical Field.