Leonhard Euler advanced every known field of mathematics in his day. A prolific author, among his greatest writings are treatises on analytic geometry, differential and integral calculus, and the calculusof variations. Euler developed spherical trigonometry, demonstrated the importance of convergence in algebraic series, proved important assertions in number theory, and made contributions to hydrodynamics, celestial mechanics, and optics. Euler also brought into common usage such mathematical notations "e" for the base of the natural logarithm, "i" for the square root of negative 1, and f(x) for a function of x. A variety of mathematical concepts bear his name, including Euler's characteristicin topology, Euler's trianglein geometry, Euler's polynomials, Euler's integrals, and Euler's constant. His accomplishments are especially remarkable in that many were made during the last quarter of his life, when he was totally blind.

Euler was born in Basel, Switzerland, on April 17, 1707 to Paul Euler and Marguerite Brucker...