# Biography of Leonard Euler

The definition of “genius” is best suited to the great mathematician and brilliant physicist Leonard Euler.

###### Childhood and early years

Euler was born on April 15, 1707 in Basel, Switzerland. His father, Paul Euler, was a pastor of the Reformed Church. His mother’s father, Margaret Brucker, was also a pastor. Leonard had two younger sisters – Anna Maria and Maria Magdalena. Soon after the birth of his son, the family moved to the town of Riyon. The boy’s father was a friend of Johann Bernoulli, a well-known European mathematician, who had a great influence on Leonard. At thirteen, Euler Jr. enters the University of Basel, and in 1723 receives a master’s degree in philosophy. In his dissertation, Euler compares the philosophy of Newton and Descartes. Johann Bernoulli, who gave the boy private lessons on Saturdays, quickly recognizes the boy’s outstanding ability for mathematics and convinces him to leave early theology and focus

In 1727, Euler took part in the competition, organized by the Paris Academy of Sciences, for the best technique for installing ship masts. Leonard takes the second place, while the first goes to Pierre Bouguer, who later becomes known as the “father of shipbuilding.” Euler takes part in this competition every year, having received twelve of these prestigious awards for his life.

###### St. Petersburg

May 17, 1727 Euler entered the medical department of the Imperial Russian Academy of Sciences in St. Petersburg, but almost immediately switched to the Faculty of Mathematics. However, because of the unrest in Russia, June 19, 1741 Euler transferred to the Berlin Academy. There the scientist will serve for about 25 years, having written more than 380 scientific articles during this time. In 1755, he was elected a foreign member of the Royal Swedish Academy of Sciences.

In the early 1760s, Euler received a proposal to teach the princess Anhalt-Dessau to the sciences, to which the scientist would write more than 200 letters that were included in the highly popular collection

The uniqueness of this work was also in the fact that in 1735 the scientist was almost completely blind to the right eye, and in 1766 his left eye was struck by cataracts. But, despite this, he continues his work and in 1755 he writes an average of one mathematical article a week.

In 1766, Euler accepted the offer to return to the St. Petersburg Academy, and spent the rest of his life in Russia. However, his second visit to this country is not so successful for him: in 1771 the fire destroys his house, and, after this, in 1773 he loses his wife to Katarina.

###### Personal life

January 7, 1734 Euler marries Catherine Gzel. In 1773, after 40 years of family life, Katarina died. Three years later, Euler marries her half-sister, Salome Abigail Gzel, with whom she will spend the rest of her life.

###### Death and heritage

September 18, 1783, after a family dinner, Euler has a cerebral hemorrhage, after which, after several hours, he dies. The scientist was buried at the Smolensk Lutheran cemetery on Vasilievsky Island, next to his first wife Katarina. In 1837, the Russian Academy of Sciences put on the bust on Leonard Euler’s grave a pedestal in the form of a rector’s chair, next to the gravestone. In 1956, on the occasion of the 250th anniversary of the birth of the scientist, the monument and remains were transferred to the cemetery of the eighteenth century under the monastery of Alexander Nevsky.

In memory of his enormous contribution to science, Euler’s portrait appeared on Swiss 10-franc banknotes of the sixth series, as well as on a number of Russian, Swiss and German brands. In his honor the asteroid “2002 Euler” is named. On May 24, the Lutheran church honors his memory on the saints calendar, as Euler was a staunch supporter of Christianity and fervently believed in the biblical commandments.

###### Mathematical Notation System

Among all the various works of Euler, the most notable is the representation of the theory of functions. He first introduced the notation f – the function “f” in the argument “x”. Euler also defined mathematical notation for trigonometric functions as we know them now, introduced the letter “e” for the base of the natural logarithm, the Greek letter “Σ” for the total sum and the letter “i” for determining the imaginary unit.

###### Analysis

Euler approved the use of exponential functions and logarithms in analytical proofs. He discovered the way to expand various logarithmic functions into a power series, and also successfully proved the application of logarithms to negative and complex numbers. Thus, Euler greatly expanded the mathematical application of logarithms.

This great mathematician also explained in detail the theory of higher transcendental functions and presented an innovative approach to solving quadratic equations. He discovered the technique of calculating integrals using complex limits. He also developed the formula of the calculus of variations, which was called the Euler-Lagrange equation.

###### Number theory

Euler proved Fermat’s small theorem, Newton’s identities, Fermat’s theorem on the sums of two squares, and also considerably advanced the proof of Lagrange’s theorem on the sum of four squares. He introduced valuable additions to the theory of perfect numbers, over which not just a mathematician worked with enthusiasm.

###### Physics and Astronomy

Euler made a significant contribution to the solution of the equation of the Euler-Bernoulli beam, which became one of the basic equations used in engineering. His scientist applied his analytical methods not only in classical mechanics, but also in solving celestial problems. For his achievements in the field of astronomy, Euler received numerous awards from the Paris Academy. Based on the knowledge of the true nature of comets and calculating the parallax of the Sun, the scientist clearly calculated the orbits of comets and other celestial bodies. With the help of these calculations, accurate tables of celestial coordinates were compiled.

**Biography of Leonard Euler**