欧拉(1707～1783年)

Euler, Leonhard

德国数学家。1733年接替丹尼尔.白努利（Daniel Bernoulli，参阅Bernoulli family）任职圣彼得堡科学院（St. Peterburg Academy of Sciences）。这期间，他发展了三角函数、对数函数和高等数学的理论。在腓特烈大帝（Frederick the Great）的邀请，成为柏林科学院（Berlin Academy）院士，在那里的二十五年中（1744～1766），发展了数学分析中函数的概念，还发现了负数的虚对数。终其一生他的兴趣都在数论（number theory）上。除了启发运用算术形式於书写数书和物理学外，欧拉引介了许多後来成为标准的符号，包括Σ为求和、e（自然对数的底）、f（函数）、i（虚数）等常用的符号以及π的应用。他对数论也十分关注，发现二次互反律，这已成为近代数论的一个重要内容。他被誉为是最伟大的数学家之一。在数学的许多分支中都有以他命名的公式、常数等等。

English version：

1707～1783年

Euler, Leonhard

German mathematician. In 1733 he succeeded Daniel Bernoulli (see Bernoulli family) at the St. Petersburg Academy of Sciences. There he developed the theory of trigonometric and logarithmic functions and advanced mathematics generally. Under the patronage of Frederick the Great, he worked at Berlin Academy for many years (1744-66), where he developed the concept of function in mathematical analysis and discovered the imaginary logarithms of negative numbers. Throughout his life he was interested in number theory. In addition to inspiring the use of arithmetic terms in writing mathematics and physics, Euler introduced many symbols that became standard, including ∑ for summation; ∫n for the sum of divisors of n; e for the base of the natural logarithm; and a, b, and c for the sides of a triangle and A, B, and C for the opposite angles; f(x) for a function; π for the ratio of the circumference to the diameter of a circle; and i for -1. Much of his work was done after he was blinded in 1766. He is considered one of the greatest mathematical minds of all time.