On the day of 242 years before the full-eye division, according to the 18th of September 1783 (August 22, 1783) the famous Swiss mathematician Leonhard Euler died. Leonhard Euler is a Swiss mathematician and physicist. He is known as one of the two greatest mathematicians in history (the other is Carl Friedrich Euler, April 5, 1707¨CSeptember 18, 1783). Leonhard Euler was the first to use the word "number" to describe a person who contains a variety of parameter expressions, such as: y=(x) (the definition of the function is given by Leibniz in 1694 and the totality of the thesis is astonished). Eura was born in Switzerland, where he was educated. Eura has always said that there is a lot of the European theology of the