Euler not only attaches importance to education, but also attaches importance to talents. At that time, Lagrange in France was only 19 years old, while Euler was 48 years old. Lagrange and Euler exchanged views on the "isoperimetric problem", and Euler was also studying this problem. Later, Lagrange made achievements, and Euler suppressed his paper and let Lagrange publish it first, which made him famous.

Euler didn't find a suitable job in Switzerland when he graduated from university at the age of 19. 1in the spring of 727, he tried to be the director of the teaching and research section in Basel, but failed. At that time, the Russian Academy of Sciences in St. Petersburg had just been established and was recruiting scientists and talents all over the country. Daniel bernoulli, who had applied to work in Petersburg, knew Euler's talent, so he tried his best to hire Euler to go to Russia. In this case, Euler left his motherland. Due to Daniel's recommendation, Euler was invited to St. Petersburg as Daniel's assistant on 1727. In St. Petersburg Academy of Sciences, he successfully obtained the position of associate professor of advanced mathematics. 173 1 was appointed as the director of the teaching and research section of theoretical physics and experimental physics. 1733, Euler, who was only 26 years old, replaced Daniel who returned to Switzerland and became a professor of mathematics and the head of the mathematics department of Petersburg Academy of Sciences.

During this period, Euler worked hard and published a large number of excellent mathematical papers, as well as other papers and works.

The foundation of classical mechanics was laid by Newton, and Euler was its main architect. 1736, Euler published "Mechanics, or the Theory of Analytically Describing Motion", in which he clearly put forward the concept of particle or particle for the first time, studied the velocity of particle moving along any curve for the first time, and applied the concept of vector to problems related to velocity and acceleration.

At the same time, he founded analytical mechanics and rigid body mechanics, and studied and developed elasticity theory, vibration theory and material mechanics. He applied vibration theory to music theory. 1739 published a book on music theory. 1738, the French Academy of Sciences set up a paper prize to answer the essence of heat, and Euler's article on fire won the prize. In this article, Euler regards the essence of heat as the vibration of molecules.

The most striking feature of Euler's research problem is that he extended his hand to the deep layer of nature and society. He is not only an outstanding mathematician, but also a master of integrating theory with practice and applying mathematics. He likes to study specific concrete problems, unlike some modern mathematicians who are tired of studying general theories.

It is precisely because the problems studied by Euler are closely related to the actual production, social needs and military needs at that time that Euler's creative talents have been fully exerted and amazing achievements have been made. While doing scientific research, Euler also applied mathematics to practice, which solved many scientific problems for the Russian government and made important contributions to society. For example, the renovation plan of the Fino Canal, the design and approval of drainage facilities in Gong Yan, the compilation of school textbooks and the government's help in drawing maps; During my work in the Weights and Measures Committee, I participated in the research on the accuracy of various weighing instruments. In addition, he also wrote comments for the publications of the Academy of Sciences and chaired the work of the Committee for a long time. He not only did a lot of work for the Academy of Sciences, but also took time to give lectures in universities, give public speeches and write popular science articles, providing astronomical data for meteorological departments and assisting construction units in mechanical analysis of design structures. 1735, Euler set out to solve an astronomical problem-calculating the orbit of comets (this problem requires the efforts of several famous mathematicians for several months). Because Euler used a new method invented by himself, it only took three days. However, three consecutive days of fatigue also made Euler break down from constant overwork, and the disease made Euler, who was only 28 years old, blind in his right eye. Such a disaster did not make Euler yield. He is still obsessed with science and works selflessly. However, due to the long-term power struggle of the Russian ruling group, it has increasingly affected Euler's work and made Euler very depressed. As it happens, Prussian King frederick the great (reign time 1740- 1786) learned about Euler's situation and invited him to Berlin. Although Euler loved his second hometown very much (where he worked and lived in Tapp in 14), he left St. Petersburg Academy of Sciences temporarily in 174 1 and took a position in Berlin Academy of Sciences as the director of the Institute of Mathematical Physics. 1759 became the leader of Berlin Academy of Sciences. While working in Berlin, he didn't forget Russia. He instructed his students in Russia through letters and sent his scientific works to Russia, which played a great role in the development of Russian science.