Leonhard euler (1April 70715 ~1September 783 18) was a Swiss mathematician and physicist. He is called one of the two greatest mathematicians in history by some mathematical historians (the other is C.F.Gauss). Euler was the first person to use the word "function" to describe expressions with various parameters, such as y = F(x) (the definition of function was given by Leibniz in 1694). He was one of the pioneers who applied calculus to physics. Euler1April 707 15 was born in Switzerland and was educated there. He spent most of his life in the Russian Empire and Prussia. Euler is a mathematical genius. As a math professor, he taught in St. Petersburg and Berlin and then returned to St. Petersburg. Euler is the mathematician with the most heritage in history, and all his works are 75 volumes. Euler actually ruled mathematics in the18th century, and he derived many results for the new invention of calculus at that time. In the last seven years of her life, Euler was completely blind. Nevertheless, he finished half his work at an amazing speed. Euler lived a pious life. However, this widely circulated legend is not true. Legend has it that Euler challenged Denis Derot in the court of Catherine II: "Sir, because (A+A+B N)/N = X；; So God exists, please answer! " Euler's death was also special: at a friend's party, he resigned and went to work, and finally left quietly on his desk. Euler is a professor at Petersburg Academy of Sciences and one of the founders of Berlin Academy of Sciences. He is the founder of rigid body mechanics and fluid mechanics, and the pioneer of the stability theory of elastic system. He thinks that the differential equation of particle dynamics can be applied to liquids (1750). He used two methods to describe the motion of fluid, that is, he described the fluid velocity field according to the fixed point in space (1755) and the determined fluid particle (1759) respectively. The former is called Euler method and the latter is called Lagrange method. Euler laid the theoretical foundation of ideal fluid, and gave the continuous equation reflecting the conservation of mass (1752) and the hydrodynamic equation reflecting the law of momentum change (1755). Euler also wrote many works on solid mechanics, such as the shape of elastic compression bar after instability, the vibration of heavy chain hanging at the upper end and so on. Euler has more than 800 monographs and papers. The asteroid Euler 2002 was named in memory of Euler.