Leonhard Euler was a Swiss mathematician who lived for most of his life in Russia. He is often regarded as the finest mathematician of his period.
Euler was the first to introduce the concept of a function, which was an enormous accomplishment at the time and laid the groundwork for all subsequent mathematical growth. He was the first to use the letter “e” to represent the base of the natural logarithm, the first to use the letter I to describe the imaginary unit, and the first to use the symbol sigma to represent summation. His work on Euler’s formula, a trigonometric equation, and Euler’s identity, ei + 1 = 0, were groundbreaking. His contribution to mathematics has been significant.