Leonhard EulerLeonhard Euler, (born April 15, 1707, died September 18, 1783), was the most prolific mathematician in history. His 866 books and articles represent about a third of all research on mathematics, theoretical physics, and engineering mechanics published between 1726 and 1800. In pure mathematics, he integrated Leibniz's differential calculus and the method Newtonian fluxions in mathematical analysis; refined the notion of function; made many mathematical notations common, including e, i, the symbol pi, and the symbol sigma; and laid the foundations for the theory of special functions, introducing the transcendent functions beta and gamma. He also worked on the origins of the calculus of variations, but held back his work in deference to JL Lagrange. He was a pioneer in the field of topology and turned number theory into a science, stating the prime number theorem and the law of biquadratic reciprocity. In physics, he articulated Newtonian dynamics and laid the foundations of analytical mechanics, notably in his Theory of the Motions of Rigid Bodies (1765). Like his teacher Johann Bernoulli, he developed the mechanics of continuous media, but he also presented the kinetic theory of gases with the molecular model. With Alexis Clairaut, he studies lunar theory. He also carried out fundamental research on elasticity, acoustics, wave theory of light and ship hydromechanics. Euler was born in Basel, Switzerland. His father, a pastor, wanted his son to follow in his footsteps and sent him to the University of Basel to prepare for the ministry, but geometry quickly became his favorite subject. Through Bernoulli's intercession, Euler obtained his father's consent to change his major to mathematics. After failing to obtain a physics position in Basel in 1726, he joined the St. Petersburg Academy of Sciences in 1727. When funds were denied to the academy, he served as a medical lieutenant in the Russian navy from 1727 to 1730. In Saint Petersburg he boarded with Bernoulli's son, Daniel. He became professor of physics at the academy in 1730 and professor of mathematics in 1733, when he married and left Bernoulli's house. His reputation grew after the publication of numerous articles and his book Mechanica (1736-37), which for the first time comprehensively presented Newtonian dynamics in the form of mathematical analysis. In 1741, Euler joined the Berlin Academy of Sciences, where he remained for 25 years. In 1744, he became director of the mathematics section of the academy. During his stay in Berlin, he wrote more than 200 articles, three books on mathematical analysis and a popular science, Letters to a Princess of Germany (3 vols., 1768-72).