289 years ago today, on January 25, 1736 (December 13, 1735 lunar calendar), Italian mathematician and mechanic Lagrange was born. Joseph Louis Lagrange (1735-1813) French mathematician and physicist. Born in Turin, Italy on January 25, 1736, and died in Paris on April 10, 1813. His father was an officer in the cavalry of the French Army. He made historic contributions in the fields of mathematics, mechanics and astronomy, with the most outstanding achievements in mathematics. At the age of 18, Lagrange wrote his first paper in Italian, which was a higher-order derivative of the product of two functions using Newton's binomial theorem. He wrote the paper in Latin and sent it to Euler, a mathematician who was then working at the Academy of Sciences in Berlin. In 1755, at the age of 19, in the process of exploring the mathematical problem "isoperiodic problem", he used Euler's ideas and results as the basis for the method of pure analysis to find the extreme value of variation. The first paper, "A Study of Maximum and Minimal Methods," developed the variation method pioneered by Euler, which laid the theoretical foundation for the variation method. The creation of the variational method made Lagrange famous in Turin, and at the age of 19 he became a professor at the Royal Artillery School in Turin, becoming the first-class mathematician recognized in Europe at that time. In 1756, on the recommendation of Euler, Lagrange was appointed a correspondent of the Prussian Academy of Sciences. In 1764, the French Academy of Sciences offered a reward for an essay to explain the lunar libration problem using gravity, and his research was awarded. Then he successfully used the theory of differential equations and approximate solutions to study a complex six-body problem proposed by the Academy of Sciences (the motion of the four moons of Jupiter), for which he was awarded again in 1766. In 1766, when Frederick the Great of Germany invited Lagrange, he said that in the court of "the greatest king in Europe" there should be "the greatest mathematician in Europe." So he was invited to Berlin, where he served as head of the mathematics department of the Prussian Academy of Sciences. He lived for 20 years, beginning the heyday of his scientific research. During this time, he completed "Analytical Mechanics", an important work on classical mechanics after Newton. In 1791, Lagrange was elected a member of the Royal Society of England. On April 3, 1813, Napoleon awarded him the Grand Cross of the Empire, but by this time Lagrange was bedridden. On the morning of April 11, Lagrange died.