Leonhard Euler
Leonhard Euler  

Born 
Basel, Switzerland  15 April 1707
Died  18 September 1783 [ OS: 7 September 1783]  (aged 76)
Alma mater  University of Basel ( MPhil) 
Known for 
Contributions Namesakes 
Spouse(s)  Katharina Gsell (1734–1773) Salome Abigail Gsell (1776–1783) 
Scientific career  
Fields  Mathematics and physics 
Institutions 
Imperial Russian Academy of Sciences Berlin Academy 
Thesis  Dissertatio physica de sono (Physical dissertation on sound) (1726) 
Doctoral advisor  Johann Bernoulli 
Doctoral students  Johann Hennert 
Other notable students 
Nicolas Fuss Stepan Rumovsky JosephLouis Lagrange (epistolary correspondent) Anders Johan Lexell 
Signature  
Notes  
He is the father of the mathematician
Johann Euler. He is listed by an academic genealogy as the equivalent to the doctoral advisor of Joseph Louis Lagrange.^{ [1]} 
Leonhard Euler ( /ˈɔɪlər/ OYlər;^{ [2]} German: [ˈɔʏlɐ] ( listen);^{ [a]} 15 April 1707 – 18 September 1783) was a Swiss mathematician, physicist, astronomer, geographer, logician and engineer who founded the studies of graph theory and topology and made pioneering and influential discoveries in many other branches of mathematics such as analytic number theory, complex analysis, and infinitesimal calculus. He introduced much of modern mathematical terminology and notation, including the notion of a mathematical function.^{ [3]} He is also known for his work in mechanics, fluid dynamics, optics, astronomy and music theory.
Euler is held to be one of the greatest mathematicians in history and the greatest of the 18th century. A statement attributed to PierreSimon Laplace expresses Euler's influence on mathematics: "Read Euler, read Euler, he is the master of us all."^{ [4]}^{ [5]} Carl Friedrich Gauss remarked: "The study of Euler's works will remain the best school for the different fields of mathematics, and nothing else can replace it."^{ [6]} Euler is also widely considered to be the most prolific; his more than 850 publications are collected in 92 quarto volumes,^{ [7]} (including his Opera Omnia) more than anyone else in the field.^{ [8]} He spent most of his adult life in Saint Petersburg, Russia, and in Berlin, then the capital of Prussia.
Euler is credited for popularizing the Greek letter π (lowercase pi) to denote Archimedes' constant (the ratio of a circle's circumference to its diameter), as well as first employing the term f(x) to describe a function's yaxis, the letter i to express the imaginary unit √1, and the Greek letter Σ (capital sigma) to express summations. He gave the current definition of the constant e, the base of the natural logarithm, still known as Euler's number.^{ [9]} Euler was also the first practitioner of graph theory (partly as a solution for the problem of the Seven Bridges of Königsberg). He became famous – among others – for solving the Basel Problem, after proving that the sum of the infinite series of squared integer reciprocals equaled exactly, π^{ 2}/6 and for discovering that the sum of the numbers of edges and faces minus vertices of a polyhedron equals 2, a number now commonly known as the Euler characteristic. In the field of physics, Euler reformulated Newton's laws of physics into new laws in his twovolume work Mechanica to explain the motion of rigid bodies more easily. He also made substantial contributions to the study of elastic deformations of solid objects.
Early life
Leonhard Euler was born on 15 April 1707, in Basel, Switzerland, to Paul III Euler, a pastor of the Reformed Church, and Marguerite ( née Brucker), another pastor's daughter. He was the oldest of four children, having two younger sisters, Anna Maria and Maria Magdalena, and a younger brother, Johann Heinrich.^{ [10]}^{ [11]} Soon after the birth of Leonhard, the Euler family moved from Basel to the town of Riehen, Switzerland, where his father became pastor in the local church and Leonhard spent most of his childhood.^{ [11]} Paul was a friend of the Bernoulli family,^{ [12]} interested in mathematics, and took classes from Jacob Bernoulli.^{ [9]} Johann Bernoulli, then regarded as Europe's foremost mathematician, would eventually be an important influence on young Leonhard.^{ [12]}
Euler's formal education started in Basel, where he was sent to live with his maternal grandmother.^{ [11]} In 1720, at only thirteen years of age, he enrolled at the University of Basel.^{ [11]} In 1723, he received a Master of Philosophy with a dissertation that compared the philosophies of René Descartes and Isaac Newton.^{ [11]} Afterwards he enrolled in the theological faculty of the University of Basel.^{ [13]} He was receiving Saturday afternoon lessons from Johann Bernoulli, who quickly discovered Euler's talent for mathematics.^{ [14]}^{ [11]} It was during this time that Euler, encouraged by the results of Johann Bernoulli's tutorial, obtained his father's consent to become a mathematician instead of a pastor.^{ [15]}^{ [13]}
In 1726, Euler completed a dissertation on the propagation of sound with the title De Sono^{ [16]}^{ [17]} with which he unsuccessfully attempted to obtain a position at the University of Basel.^{ [18]} In 1727, he entered the Paris Academy prize competition (offered annually and later biennially by the academy beginning in 1720)^{ [19]} for the first time. The problem that year was to find the best way to place the masts on a ship. Pierre Bouguer, who became known as "the father of naval architecture", won and Euler took second place.^{ [20]} Euler eventually entered this competition 15 times,^{ [19]} winning 12 of them.^{ [20]}
Career
Saint Petersburg
Johann Bernoulli's two sons, Daniel and Nicolaus, entered into service at the Imperial Russian Academy of Sciences in Saint Petersburg in 1725, leaving Euler with the assurance they'd recommend him to a post when one was available.^{ [18]} On 31 July 1726, Nicolaus died of appendicitis after spending less than a year in Russia.^{ [21]}^{ [22]} When Daniel assumed his brother's position in the mathematics/physics division, he recommended that the post in physiology that he had vacated be filled by his friend Euler.^{ [18]} In November 1726 Euler eagerly accepted the offer, but delayed making the trip to Saint Petersburg while he unsuccessfully applied for a physics professorship at the University of Basel.^{ [18]}
Euler arrived in Saint Petersburg in May 1727.^{ [18]}^{ [13]} He was promoted from his junior post in the medical department of the academy to a position in the mathematics department. He lodged with Daniel Bernoulli with whom he worked in close collaboration.^{ [23]} Euler mastered Russian, settled into life in Saint Petersburg and took on an additional job as a medic in the Russian Navy.^{ [24]}
The Academy at Saint Petersburg, established by Peter the Great, was intended to improve education in Russia and to close the scientific gap with Western Europe. As a result, it was made especially attractive to foreign scholars like Euler.^{ [20]} The Academy's benefactress, Catherine I, who had continued the progressive policies of her late husband, died before Euler's arrival to Saint Petersburg.^{ [25]} The Russian conservative nobility then gained power upon the ascension of the twelveyearold Peter II.^{ [25]} The nobility, suspicious of the academy's foreign scientists, cut funding for Euler and his colleagues and prevented the entrance of foreign and nonaristocratic students into the Gymnasium and Universities.^{ [25]}
Conditions improved slightly after the death of Peter II in 1730 and the Germaninfluenced Anna of Russia assumed.^{ [26]} Euler swiftly rose through the ranks in the academy and was made a professor of physics in 1731.^{ [26]} He also left the Russian Navy, refusing a promotion to a lieutenant.^{ [26]} Two years later, Daniel Bernoulli, fed up with the censorship and hostility he faced at Saint Petersburg, left for Basel. Euler succeeded him as the head of the mathematics department.^{ [27]} In January 1734, he married Katharina Gsell (1707–1773), a daughter of Georg Gsell.^{ [28]} Frederick II has made an attempt to recruit the services of Euler for his newly established Berlin Academy in 1740, but Euler initially preferred to stay in St Petersburg.^{ [29]} But after Emperor Anna died and Frederick II agreed to pay 1600 Ecus (the same as Euler earned in Russia) he agreed to move to Berlin. In 1741, he requested for permission to leave to Berlin, arguing he was in need for a milder climate for his eyesight.^{ [29]} The Russian academy gave its consent and would pay him 200 Rubles per year as one of its active members.^{ [29]}
Berlin
Concerned about the continuing turmoil in Russia, Euler left St. Petersburg in June 1741 to take up a post at the Berlin Academy, which he had been offered by Frederick the Great of Prussia.^{ [30]} He lived for 25 years in Berlin, where he wrote several hundred articles.^{ [13]} In 1748 his text on functions called the Introductio in analysin infinitorum was published and in 1755 a text on differential calculus called the Institutiones calculi differentialis was published.^{ [31]}^{ [32]} In 1755, he was elected a foreign member of the Royal Swedish Academy of Sciences^{ [33]} and of the French Academy of Sciences.^{ [34]} Notable students of Euler in Berlin included Stepan Rumovsky, later considered as the first Russian astronomer.^{ [35]}^{ [36]} In 1748 he declined an offer from the University of Basel to succeed the recently deceased Johann Bernoulli.^{ [13]} In 1753 he bought a house in Charlottenburg, in which he lived with his family and widowed mother.^{ [37]}^{ [38]}
Euler became the tutor for Friederike Charlotte of BrandenburgSchwedt, the Princess of AnhaltDessau and Frederick's niece. He wrote over 200 letters to her in the early 1760s, which were later compiled into a volume entitled Letters of Euler on different Subjects in Natural Philosophy Addressed to a German Princess.^{ [39]} This work contained Euler's exposition on various subjects pertaining to physics and mathematics and offered valuable insights into Euler's personality and religious beliefs. It was translated into multiple languages, published across Europe and in the United States, and became more widely read than any of his mathematical works. The popularity of the Letters testifies to Euler's ability to communicate scientific matters effectively to a lay audience, a rare ability for a dedicated research scientist.^{ [32]}
Despite Euler's immense contribution to the Academy's prestige and having been put forward as a candidate for its presidency by Jean le Rond d'Alembert, Frederick II named himself as its president.^{ [38]} The Prussian king had a large circle of intellectuals in his court, and he found the mathematician unsophisticated and illinformed on matters beyond numbers and figures. Euler was a simple, devoutly religious man who never questioned the existing social order or conventional beliefs, in many ways the polar opposite of Voltaire, who enjoyed a high place of prestige at Frederick's court. Euler was not a skilled debater and often made it a point to argue subjects that he knew little about, making him the frequent target of Voltaire's wit.^{ [32]} Frederick also expressed disappointment with Euler's practical engineering abilities, stating:
I wanted to have a water jet in my garden: Euler calculated the force of the wheels necessary to raise the water to a reservoir, from where it should fall back through channels, finally spurting out in Sanssouci. My mill was carried out geometrically and could not raise a mouthful of water closer than fifty paces to the reservoir. Vanity of vanities! Vanity of geometry!^{ [40]}
Throughout his stay in Berlin, he maintained a strong connection to the Academy in St. Petersburg and also published 109 papers in Russia.^{ [41]} He also assisted students from the Academy in St. Petersburg and at times accommodated Russian students in his house in Berlin.^{ [41]} In 1760, with the Seven Years' War raging, Euler's farm in Charlottenburg was sacked by advancing Russian troops.^{ [37]} Upon learning of this event, General Ivan Petrovich Saltykov paid compensation for the damage caused to Euler's estate, with Empress Elizabeth of Russia later adding a further payment of 4000 roubles—an exorbitant amount at the time.^{ [42]} Euler decided to leave Berlin in 1766 and return to Russia.^{ [43]}
Return to Russia
The political situation in Russia stabilized after Catherine the Great's accession to the throne, so in 1766 Euler accepted an invitation to return to the St. Petersburg Academy. His conditions were quite exorbitant—a 3000 ruble annual salary, a pension for his wife, and the promise of highranking appointments for his sons. At the university he was assisted by his student Anders Johan Lexell.^{ [44]} While living in St. Petersburg, a fire in 1771 destroyed his home.^{ [45]}
Personal life
On 7 January 1734, he married Katharina Gsell (1707–1773), daughter of Georg Gsell, a painter from the Academy Gymnasium in Saint Petersburg.^{ [28]} The young couple bought a house by the Neva River. Of their thirteen children, only five survived childhood,^{ [46]} three sons and two daughters.^{ [47]} Their first son was Johann Albrecht Euler, whose godfather was Christian Goldbach.^{ [47]} Three years after his wife's death in 1773,^{ [45]} Euler married her halfsister, Salome Abigail Gsell (1723–1794).^{ [48]} This marriage lasted until his death in 1783. His brother Johann Heinrich has settled in the St. Petersburg in 1735 and was employed as a painter at the Academy.^{ [29]}
Death
In St. Petersburg on 18 September 1783, after a lunch with his family, Euler was discussing the newly discovered planet Uranus and its orbit with Lexell when he collapsed and died from a brain hemorrhage.^{ [49]} Jacob von Staehlin wrote a short obituary for the Russian Academy of Sciences and Russian mathematician Nicolas Fuss, one of Euler's disciples, wrote a more detailed eulogy,^{ [46]} which he delivered at a memorial meeting. In his eulogy for the French Academy, French mathematician and philosopher Marquis de Condorcet, wrote:
il cessa de calculer et de vivre— ... he ceased to calculate and to live.^{ [50]}
Euler was buried next to Katharina at the Smolensk Lutheran Cemetery on Vasilievsky Island. In 1837, the Russian Academy of Sciences installed a new monument, replacing his overgrown grave plaque. To commemorate the 250th anniversary of Euler's birth in 1957, his tomb was moved to the Lazarevskoe Cemetery at the Alexander Nevsky Monastery.^{ [51]}
Eyesight deterioration
Euler's eyesight worsened throughout his mathematical career. In 1738, three years after nearly expiring from fever,^{ [52]} he became almost blind in his right eye. Euler blamed the cartography he performed for the St. Petersburg Academy for his condition,^{ [53]} but the cause of his blindness remains the subject of speculation.^{ [49]} Euler's vision in that eye worsened throughout his stay in Germany, to the extent that Frederick referred to him as " Cyclops". Euler remarked on his loss of vision, stating "Now I will have fewer distractions."^{ [53]} In 1766 a cataract in his left eye was discovered, and a few weeks later a failed surgical restoration rendered him almost totally blind. However, his condition appeared to have little effect on his productivity. With the aid of his scribes, Euler's productivity in many areas of study increased^{ [54]} and in 1775 he produced, on average, one mathematical paper every week.^{ [34]}
Contributions to mathematics and physics
Part of a series of articles on the 
mathematical constant e 

Properties 
Applications 
Defining e 
People 
Related topics 
Euler worked in almost all areas of mathematics, such as geometry, infinitesimal calculus, trigonometry, algebra, and number theory, as well as continuum physics, lunar theory and other areas of physics. He is a seminal figure in the history of mathematics; if printed, his works, many of which are of fundamental interest, would occupy between 60 and 80 quarto volumes.^{ [34]} Euler's name is associated with a large number of topics.
Mathematical notation
Euler introduced and popularized several notational conventions through his numerous and widely circulated textbooks. Most notably, he introduced the concept of a function^{ [3]} and was the first to write f(x) to denote the function f applied to the argument x. He also introduced the modern notation for the trigonometric functions, the letter e for the base of the natural logarithm (now also known as Euler's number), the Greek letter Σ for summations and the letter i to denote the imaginary unit.^{ [55]} The use of the Greek letter π to denote the ratio of a circle's circumference to its diameter was also popularized by Euler, although it originated with Welsh mathematician William Jones.^{ [56]}
Analysis
The development of infinitesimal calculus was at the forefront of 18thcentury mathematical research, and the Bernoullis—family friends of Euler—were responsible for much of the early progress in the field. Thanks to their influence, studying calculus became the major focus of Euler's work. While some of Euler's proofs are not acceptable by modern standards of mathematical rigour^{ [57]} (in particular his reliance on the principle of the generality of algebra), his ideas led to many great advances. Euler is well known in analysis for his frequent use and development of power series, the expression of functions as sums of infinitely many terms,^{ [58]} such as
Euler's use of power series enabled him to solve the famous Basel problem in 1735 (he provided a more elaborate argument in 1741):^{ [57]}
Euler introduced the use of the exponential function and logarithms in analytic proofs. He discovered ways to express various logarithmic functions using power series, and he successfully defined logarithms for negative and complex numbers, thus greatly expanding the scope of mathematical applications of logarithms.^{ [55]} He also defined the exponential function for complex numbers and discovered its relation to the trigonometric functions. For any real number φ (taken to be radians), Euler's formula states that the complex exponential function satisfies
Euler elaborated the theory of higher transcendental functions by introducing the gamma function^{ [61]}^{ [62]} and introduced a new method for solving quartic equations.^{ [63]} He found a way to calculate integrals with complex limits, foreshadowing the development of modern complex analysis. He invented the calculus of variations and formulated the Euler–Lagrange equation for reducing optimization problems in this area to the solution of differential equations.
Euler pioneered the use of analytic methods to solve number theory problems. In doing so, he united two disparate branches of mathematics and introduced a new field of study, analytic number theory. In breaking ground for this new field, Euler created the theory of hypergeometric series, qseries, hyperbolic trigonometric functions and the analytic theory of continued fractions. For example, he proved the infinitude of primes using the divergence of the harmonic series, and he used analytic methods to gain some understanding of the way prime numbers are distributed. Euler's work in this area led to the development of the prime number theorem.^{ [64]}
Number theory
Euler's interest in number theory can be traced to the influence of Christian Goldbach,^{ [65]} his friend in the St. Petersburg Academy.^{ [52]} Much of Euler's early work on number theory was based on the work of Pierre de Fermat. Euler developed some of Fermat's ideas and disproved some of his conjectures, such as his conjecture that all numbers of the form ( Fermat numbers) are prime.^{ [66]}
Euler linked the nature of prime distribution with ideas in analysis. He proved that the sum of the reciprocals of the primes diverges. In doing so, he discovered the connection between the Riemann zeta function and the prime numbers; this is known as the Euler product formula for the Riemann zeta function.^{ [67]}
Euler invented the totient function φ(n), the number of positive integers less than or equal to the integer n that are coprime to n. Using properties of this function, he generalized Fermat's little theorem to what is now known as Euler's theorem.^{ [68]} He contributed significantly to the theory of perfect numbers, which had fascinated mathematicians since Euclid. He proved that the relationship shown between even perfect numbers and Mersenne primes earlier proved by Euclid was onetoone, a result otherwise known as the Euclid–Euler theorem.^{ [69]} Euler also conjectured the law of quadratic reciprocity. The concept is regarded as a fundamental theorem of number theory, and his ideas paved the way for the work of Carl Friedrich Gauss, particularly Disquisitiones Arithmeticae.^{ [70]} By 1772 Euler had proved that 2^{31} − 1 = 2,147,483,647 is a Mersenne prime. It may have remained the largest known prime until 1867.^{ [71]}
Euler contributed major developments to the theory of partitions of an integer.^{ [72]}
Graph theory
In 1735, Euler presented a solution to the problem known as the Seven Bridges of Königsberg.^{ [73]} The city of Königsberg, Prussia was set on the Pregel River, and included two large islands that were connected to each other and the mainland by seven bridges. The problem is to decide whether it is possible to follow a path that crosses each bridge exactly once and returns to the starting point. It is not possible: there is no Eulerian circuit. This solution is considered to be the first theorem of graph theory.^{ [73]}
Euler also discovered the formula relating the number of vertices, edges and faces of a convex polyhedron,^{ [74]} and hence of a planar graph. The constant in this formula is now known as the Euler characteristic for the graph (or other mathematical object), and is related to the genus of the object.^{ [75]} The study and generalization of this formula, specifically by Cauchy^{ [76]} and L'Huilier,^{ [77]} is at the origin of topology.^{ [74]}
Physics, astronomy, and engineering
Part of a series on 
Classical mechanics 

Some of Euler's greatest successes were in solving realworld problems analytically, and in describing numerous applications of the Bernoulli numbers, Fourier series, Euler numbers, the constants e and π, continued fractions and integrals. He integrated Leibniz's differential calculus with Newton's Method of Fluxions, and developed tools that made it easier to apply calculus to physical problems. He made great strides in improving the numerical approximation of integrals, inventing what are now known as the Euler approximations. The most notable of these approximations are Euler's method^{ [78]} and the Euler–Maclaurin formula.^{ [79]}^{ [80]}^{ [81]}
Euler helped develop the Euler–Bernoulli beam equation, which became a cornerstone of engineering.^{ [82]} Besides successfully applying his analytic tools to problems in classical mechanics, Euler applied these techniques to celestial problems. His work in astronomy was recognized by multiple Paris Academy Prizes over the course of his career. His accomplishments include determining with great accuracy the orbits of comets and other celestial bodies, understanding the nature of comets, and calculating the parallax of the Sun. His calculations contributed to the development of accurate longitude tables.^{ [83]}
Euler made important contributions in optics.^{ [84]} He disagreed with Newton's corpuscular theory of light,^{ [85]} which was then the prevailing theory. His 1740s papers on optics helped ensure that the wave theory of light proposed by Christiaan Huygens would become the dominant mode of thought, at least until the development of the quantum theory of light.^{ [86]}
In fluid dynamics, Euler was the first to predict the phenomenon of cavitation, in 1754, long before its first observation in the late 19th century, and the Euler number used in fluid flow calculations comes from his related work on the efficiency of turbines.^{ [87]} In 1757 he published an important set of equations for inviscid flow in fluid dynamics, that are now known as the Euler equations.^{ [88]}
Euler is well known in structural engineering for his formula giving Euler's critical load, the critical buckling load of an ideal strut, which depends only on its length and flexural stiffness.^{ [89]}
Logic
Euler is credited with using closed curves to illustrate syllogistic reasoning (1768). These diagrams have become known as Euler diagrams.^{ [90]}
An Euler diagram is a diagrammatic means of representing sets and their relationships. Euler diagrams consist of simple closed curves (usually circles) in the plane that depict sets. Each Euler curve divides the plane into two regions or "zones": the interior, which symbolically represents the elements of the set, and the exterior, which represents all elements that are not members of the set. The sizes or shapes of the curves are not important; the significance of the diagram is in how they overlap. The spatial relationships between the regions bounded by each curve (overlap, containment or neither) corresponds to settheoretic relationships ( intersection, subset and disjointness). Curves whose interior zones do not intersect represent disjoint sets. Two curves whose interior zones intersect represent sets that have common elements; the zone inside both curves represents the set of elements common to both sets (the intersection of the sets). A curve that is contained completely within the interior zone of another represents a subset of it.
Euler diagrams (and their refinement to Venn diagrams) were incorporated as part of instruction in set theory as part of the new math movement in the 1960s.^{ [91]} Since then, they have come into wide use as a way of visualizing combinations of characteristics.^{ [92]}
Music
One of Euler's more unusual interests was the application of mathematical ideas in music. In 1739 he wrote the Tentamen novae theoriae musicae (Attempt at a New Theory of Music), hoping to eventually incorporate musical theory as part of mathematics. This part of his work, however, did not receive wide attention and was once described as too mathematical for musicians and too musical for mathematicians.^{ [93]} Even when dealing with music, Euler's approach is mainly mathematical,^{ [94]} including for instance the introduction of binary logarithms as a way of describing numerically the subdivision of octaves into fractional parts.^{ [95]} His writings on music are not particularly numerous (a few hundred pages, in his total production of about thirty thousand pages), but they reflect an early preoccupation and one that did not leave him throughout his life.^{ [94]}
A first point of Euler's musical theory is the definition of "genres", i.e. of possible divisions of the octave using the prime numbers 3 and 5. Euler describes 18 such genres, with the general definition 2^{m}A, where A is the "exponent" of the genre (i.e. the sum of the exponents of 3 and 5) and 2^{m} (where "m is an indefinite number, small or large, so long as the sounds are perceptible"^{ [96]}), expresses that the relation holds independently of the number of octaves concerned. The first genre, with A = 1, is the octave itself (or its duplicates); the second genre, 2^{m}.3, is the octave divided by the fifth (fifth + fourth, C–G–C); the third genre is 2^{m}.5, major third + minor sixth (C–E–C); the fourth is 2^{m}.3^{2}, twofourths and a tone (C–F–B♭–C); the fifth is 2^{m}.3.5 (C–E–G–B–C); etc. Genres 12 (2^{m}.3^{3}.5), 13 (2^{m}.3^{2}.5^{2}) and 14 (2^{m}.3.5^{3}) are corrected versions of the diatonic, chromatic and enharmonic, respectively, of the Ancients. Genre 18 (2^{m}.3^{3}.5^{2}) is the "diatonicochromatic", "used generally in all compositions",^{ [97]} and which turns out to be identical with the system described by Johann Mattheson.^{ [98]} Euler later envisaged the possibility of describing genres including the prime number 7.^{ [99]}
Euler devised a specific graph, the Speculum musicum,^{ [100]} to illustrate the diatonicochromatic genre, and discussed paths in this graph for specific intervals, recalling his interest in the Seven Bridges of Königsberg (see above). The device drew renewed interest as the Tonnetz in neoRiemannian theory (see also Lattice (music)).^{ [101]}
Euler further used the principle of the "exponent" to propose a derivation of the gradus suavitatis (degree of suavity, of agreeableness) of intervals and chords from their prime factors – one must keep in mind that he considered just intonation, i.e. 1 and the prime numbers 3 and 5 only.^{ [102]} Formulas have been proposed extending this system to any number of prime numbers, e.g. in the form
Personal philosophy and religious beliefs
Euler opposed the concepts of Leibniz's monadism and the philosophy of Christian Wolff.^{ [104]} Euler insisted that knowledge is founded in part on the basis of precise quantitative laws, something that monadism and Wolffian science were unable to provide. Euler's religious leanings might also have had a bearing on his dislike of the doctrine; he went so far as to label Wolff's ideas as "heathen and atheistic".^{ [105]}
Euler stayed a religious person throughout his life.^{ [13]} Much of what is known of Euler's religious beliefs can be deduced from his Letters to a German Princess and an earlier work, Rettung der Göttlichen Offenbahrung gegen die Einwürfe der Freygeister (Defense of the Divine Revelation against the Objections of the Freethinkers). These works show that Euler was a devout Christian who believed the Bible to be inspired; the Rettung was primarily an argument for the divine inspiration of scripture.^{ [106]}^{ [107]}
There is a famous legend^{ [108]} inspired by Euler's arguments with secular philosophers over religion, which is set during Euler's second stint at the St. Petersburg Academy. The French philosopher Denis Diderot was visiting Russia on Catherine the Great's invitation. However, the Empress was alarmed that the philosopher's arguments for atheism were influencing members of her court, and so Euler was asked to confront the Frenchman. Diderot was informed that a learned mathematician had produced a proof of the existence of God: he agreed to view the proof as it was presented in court. Euler appeared, advanced toward Diderot, and in a tone of perfect conviction announced this nonsequitur: "Sir, a+b^{n}/n=x, hence God exists—reply!" Diderot, to whom (says the story) all mathematics was gibberish, stood dumbstruck as peals of laughter erupted from the court. Embarrassed, he asked to leave Russia, a request that was graciously granted by the Empress. However amusing the anecdote may be, it is apocryphal, given that Diderot himself did research in mathematics.^{ [109]} The legend was apparently first told by Dieudonné Thiébault with embellishment by Augustus De Morgan.^{ [108]}
Commemorations
Euler was featured on both the sixth^{ [110]} and seventh^{ [111]} series of the Swiss 10 franc banknote and on numerous Swiss, German, and Russian postage stamps. In 1782 he was elected a Foreign Honorary Member of the American Academy of Arts and Sciences.^{ [112]} The asteroid 2002 Euler was named in his honour.^{ [113]}
Selected bibliography
Euler has an extensive bibliography. His books include:
 Mechanica (1736).
 Methodus inveniendi lineas curvas maximi minimive proprietate gaudentes, sive solutio problematis isoperimetrici latissimo sensu accepti (1744).^{ [114]} Latin translation: a method for finding curved lines enjoying properties of maximum or minimum, or solution of isoperimetric problems in the broadest accepted sense.^{ [115]}
 Introductio in analysin infinitorum (1748).^{ [116]}^{ [117]} English translation: Introduction to Analysis of the Infinite^{ [118]}
 Institutiones calculi differentialis (1755).^{ [117]}^{ [119]}
 Vollständige Anleitung zur Algebra (1765).
 Institutiones calculi integralis (1768–1770).^{ [117]}
 Letters to a German Princess (1768–1772).^{ [32]}
 Dioptrica, published in three volumes beginning in 1769.^{ [84]}
It took until 1830 for the bulk of Euler's posthumous works to be individually published,^{ [120]} with an additional batch of 61 unpublished works discovered by Paul Heinrich von Fuss, Euler's greatgrandson and Nicolas Fuss's son, and published as a collection in 1862.^{ [120]}^{ [121]} After several delays in the 19th century,^{ [120]} a definitive collection of Euler's works, entitled Opera Omnia, has been published since 1911 by the Euler Commission of the Swiss Academy of Sciences.^{ [122]} A chronological catalog of Euler's works was compiled by Swedish mathematician Gustaf Eneström and published from 1910 to 1913,^{ [123]} and Euler's works are often cited by their number in the Eneström index, from E1 to E866.^{ [124]} The Euler Archive was started at Dartmouth College^{ [125]} before moving to the Mathematical Association of America^{ [126]} and, most recently, to University of the Pacific in 2017.^{ [127]}
Illustration from Solutio problematis... a. 1743 propositi published in Acta Eruditorum, 1744
Notes
References
 ^ Leonhard Euler at the Mathematics Genealogy Project Retrieved 2 July 2021

^ The pronunciation
/ˈjuːlər/ is incorrect. See:
 "Euler". Oxford English Dictionary (2nd ed.). Oxford University Press. 1989.
 "Euler". Merriam–Webster's Online Dictionary. 2009. Archived from the original on 25 April 2009. Retrieved 5 June 2009.
 "Euler, Leonhard". The American Heritage Dictionary of the English Language (5th ed.). Boston: Houghton Mifflin Company. 2011. Archived from the original on 4 October 2013. Retrieved 30 May 2013.
 Peter M. Higgins (2007). Nets, Puzzles, and Postmen: An Exploration of Mathematical Connections. Oxford University Press. p. 43. ISBN 9780199218424.
 ^ ^{a} ^{b} Dunham 1999, p. 17.
 ^ Dunham 1999, p. xiii "Lisez Euler, lisez Euler, c'est notre maître à tous."
 ^ The quote appeared in Gugliemo Libri's review of a recently published collection of correspondence among eighteenthcentury mathematicians: Libri, Gugliemo (January 1846). "Correspondance mathématique et physique de quelques célèbres géomètres du XVIIIe siècle, ..." [Mathematical and physical correspondence of some famous geometers of the eighteenth century, ...]. Journal des Savants (in French): 51. Archived from the original on 9 August 2018. Retrieved 7 April 2014. "... nous rappellerions que Laplace lui même, ... ne cessait de répéter aux jeunes mathématiciens ces paroles mémorables que nous avons entendues de sa propre bouche : 'Lisez Euler, lisez Euler, c'est notre maître à tous.' " [... we would recall that Laplace himself, ... never ceased to repeat to young mathematicians these memorable words that we heard from his own mouth: 'Read Euler, read Euler, he is our master in everything.]
 ^ Grinstein, Louise; Lipsey, Sally I. (2001). "Euler, Leonhard (1707–1783)". Encyclopedia of Mathematics Education. Routledge. p. 235. ISBN 9780415763684.
 ^ "The Euler Archive". eulerarchive.maa.org. Archived from the original on 28 August 2021. Retrieved 19 February 2014.
 ^ Gautschi 2008, p. 3.
 ^ ^{a} ^{b} Boyer, Carl B (1 June 2021). "Leonhard Euler". Encyclopedia Britannica. Archived from the original on 3 May 2021. Retrieved 27 May 2021.
 ^ Calinger 2016, p. 11.
 ^ ^{a} ^{b} ^{c} ^{d} ^{e} ^{f} Gautschi 2008, p. 4.
 ^ ^{a} ^{b} Calinger 1996, pp. 124–125.
 ^ ^{a} ^{b} ^{c} ^{d} ^{e} ^{f} Knobloch, Eberhard, ed. (May 1983). Zum Werk Leonhard Eulers: Vorträge des EulerKolloquiums im Mai 1983 in Berlin (PDF). Springer Publishing. Birkhäuser Verlag. doi: 10.1007/9783034871211. ISBN 9783034871228.
 ^ James, Ioan (2002). Remarkable Mathematicians: From Euler to von Neumann. Cambridge University Press. p. 2. ISBN 9780521520942.
 ^ Calinger 1996, p. 124.
 ^ Calinger 2016, p. 32.
 ^ Euler, Leonhard (1727). Dissertatio physica de sono [Physical dissertation on sound] (in Latin). Basel: E. and J. R. Thurnisiorum. Archived from the original on 6 June 2021. Retrieved 6 June 2021 – via Euler archive. Translated into English as Bruce, Ian. "Euler's Dissertation De Sono : E002" (PDF). Some Mathematical Works of the 17th & 18th Centuries, including Newton's Principia, Euler's Mechanica, Introductio in Analysin, etc., translated mainly from Latin into English. Archived (PDF) from the original on 10 June 2016. Retrieved 12 June 2021.
 ^ ^{a} ^{b} ^{c} ^{d} ^{e} Calinger 1996, p. 125.
 ^ ^{a} ^{b} "The Paris Academy". Euler Archive. Mathematical Association of America. Archived from the original on 30 July 2021. Retrieved 29 July 2021.
 ^ ^{a} ^{b} ^{c} Calinger 1996, p. 156.
 ^ Calinger 1996, pp. 121–166.
 ^ O'Connor, John J.; Robertson, Edmund F. "Nicolaus (II) Bernoulli". MacTutor History of Mathematics archive. University of St Andrews. Retrieved 2 July 2021.
 ^ Calinger 1996, pp. 126–127.
 ^ Calinger 1996, p. 127.
 ^ ^{a} ^{b} ^{c} Calinger 1996, p. 126.
 ^ ^{a} ^{b} ^{c} Calinger 1996, p. 128.
 ^ Calinger 1996, pp. 128–29.
 ^ ^{a} ^{b} Gekker & Euler 2007, p. 402.
 ^ ^{a} ^{b} ^{c} ^{d} Calinger 1996, pp. 157–158.
 ^ Gautschi 2008, p. 7.
 ^ Euler, Leonhard (1787). "Institutiones calculi differentialis cum eius usu in analysi finitorum ac doctrina serierum" [Foundations of Differential Calculus, with Applications to Finite Analysis and Series]. Academiae Imperialis Scientiarum Petropolitanae (in Latin). Petri Galeatii. 1: 1–880. Archived from the original on 6 May 2021. Retrieved 8 June 2021 – via Euler archive.
 ^ ^{a} ^{b} ^{c} ^{d} Dunham 1999, pp. xxiv–xxv.
 ^ Stén, Johan C.E. (2014). "Academic events in Saint Petersburg". A Comet of the Enlightenment. Vita Mathematica. 17. Birkhäuser. pp. 119–135. doi: 10.1007/9783319006185_7. See in particular footnote 37, p. 131.
 ^ ^{a} ^{b} ^{c} Finkel, B. F. (1897). "Biography – Leonard Euler". The American Mathematical Monthly. 4 (12): 297–302. doi: 10.2307/2968971. JSTOR 2968971. MR 1514436.
 ^ Biographical Encyclopedia of Astronomers. Springer. 18 September 2007. p. 992. ISBN 9780387304007. Archived from the original on 22 April 2021. Retrieved 15 June 2021.
 ^ Clark, William; Golinski, Jan; Schaffer, Simon (1 July 1999). The Sciences in Enlightened Europe. University of Chicago Press. p. 395. ISBN 9780226109404. Archived from the original on 22 April 2021. Retrieved 15 June 2021.
 ^ ^{a} ^{b} Knobloch, Eberhard (2007). ""Leonhard Euler 1707–1783. Zum 300. Geburtstag eines langjährigen Wahlberliners"". Mitteilungen der Deutschen MathematikerVereinigung. 15 (4): 276–288. doi: 10.1515/dmvm20070092. S2CID 122271644.
 ^ ^{a} ^{b} Gautschi 2008, pp. 8–9.
 ^ Euler, Leonhard (1802). Letters of Euler on Different Subjects of Physics and Philosophy, Addressed to a German Princess. Translated by Hunter, Henry (2nd ed.). London: Murray and Highley – via Internet Archive.
 ^ Frederick II of Prussia (1927). Letters of Voltaire and Frederick the Great, Letter H 7434, 25 January 1778. Richard Aldington. New York: Brentano's.
 ^ ^{a} ^{b} Vucinich, Alexander (1960). "Mathematics in Russian Culture". Journal of the History of Ideas. 21 (2): 164–165. doi: 10.2307/2708192. ISSN 00225037. JSTOR 2708192. Archived from the original on 3 August 2021. Retrieved 3 August 2021 – via JSTOR.
 ^ Gindikin, Simon (2007). "Leonhard Euler". Tales of Mathematicians and Physicists. Springer. pp. 171–212. doi: 10.1007/9780387488110_7. ISBN 9780387488110. See in particular p. 182 Archived 10 June 2021 at the Wayback Machine.
 ^ Gautschi 2008, p. 9.
 ^ Maehara, Hiroshi; Martini, Horst (2017). "On Lexell's Theorem". The American Mathematical Monthly. 124 (4): 337–344. doi: 10.4169/amer.math.monthly.124.4.337. ISSN 00029890. JSTOR 10.4169/amer.math.monthly.124.4.337. S2CID 125175471. Archived from the original on 20 August 2021. Retrieved 16 June 2021.
 ^ ^{a} ^{b} Thiele, Rüdiger (2005). "The mathematics and science of Leonhard Euler". In Kinyon, Michael; van Brummelen, Glen (eds.). Mathematics and the Historian's Craft: The Kenneth O. May Lectures. Springer. pp. 81–140. ISBN 9780387252841.
 ^ ^{a} ^{b} Fuss, Nicolas (1783). "Éloge de M. Léonhard Euler" [Eulogy for Leonhard Euler]. Nova Acta Academiae Scientiarum Imperialis Petropolitanae (in French). 1: 159–212. Archived from the original on 20 August 2021. Retrieved 19 May 2018 – via Bioheritage Diversity Library. Translated into English as "Eulogy of Leonhard Euler by Nicolas Fuss". MacTutor History of Mathematics Archive. Translated by Glaus, John S. D. St Andrews University. Archived from the original on 26 December 2018. Retrieved 30 August 2006.
 ^ ^{a} ^{b} Calinger 1996, p. 129.
 ^ Gekker & Euler 2007, p. 405.
 ^ ^{a} ^{b} Asensi, Victor; Asensi, Jose M. (March 2013). "Euler's right eye: the dark side of a bright scientist". Clinical Infectious Diseases. 57 (1): 158–159. doi: 10.1093/cid/cit170. PMID 23487386.
 ^ Marquis de Condorcet. "Eulogy of Euler – Condorcet". Archived from the original on 16 September 2006. Retrieved 30 August 2006.
 ^ Calinger 2016, pp. 530–536.
 ^ ^{a} ^{b} Gautschi 2008, p. 6.
 ^ ^{a} ^{b} Eves, Howard W. (1969). "Euler's blindness". In Mathematical Circles: A Selection of Mathematical Stories and Anecdotes, Quadrants III and IV. Prindle, Weber, & Schmidt. p. 48. Also quoted by Richeson (2012), p. 17 Archived 16 June 2021 at the Wayback Machine, cited to Eves.
 ^ Gautschi 2008, pp. 9–10.
 ^ ^{a} ^{b} Boyer, Carl B.; Merzbach, Uta C. (1991). A History of Mathematics. John Wiley & Sons. pp. 439–45. ISBN 9780471543978.
 ^ Arndt, Jörg; Haenel, Christoph (2006). Pi Unleashed. SpringerVerlag. p. 166. ISBN 9783540665724. Archived from the original on 17 June 2021. Retrieved 8 June 2021.
 ^ ^{a} ^{b} Wanner, Gerhard; Hairer, Ernst (2005). Analysis by its history (1st ed.). Springer. p. 63. ISBN 9780387770369.
 ^ Ferraro 2008, p. 155.
 ^ Lagarias, Jeffrey C. (October 2013). "Euler's constant: Euler's work and modern developments". Bulletin of the American Mathematical Society. 50 (4): 556. arXiv: 1303.1856. doi: 10.1090/s02730979201301423x. MR 3090422. S2CID 119612431.
 ^ Feynman, Richard (1970). "Chapter 22: Algebra". The Feynman Lectures on Physics. I. p. 10.
 ^ Ferraro 2008, p. 159.
 ^ Davis, Philip J. (1959). "Leonhard Euler's integral: A historical profile of the gamma function". The American Mathematical Monthly. 66: 849–869. doi: 10.2307/2309786. JSTOR 2309786. MR 0106810.
 ^ Nickalls, R. W. D. (March 2009). "The quartic equation: invariants and Euler's solution revealed". The Mathematical Gazette. 93 (526): 66–75. doi: 10.1017/S0025557200184190. JSTOR 40378672. S2CID 16741834.
 ^ Dunham 1999, Ch. 3, Ch. 4.
 ^ Calinger 1996, p. 130.
 ^ Dunham 1999, p. 7.
 ^ Patterson, S. J. (1988). An introduction to the theory of the Riemann zetafunction. Cambridge Studies in Advanced Mathematics. 14. Cambridge: Cambridge University Press. p. 1. doi: 10.1017/CBO9780511623707. ISBN 9780521335355. MR 0933558. Archived from the original on 18 June 2021. Retrieved 6 June 2021.
 ^ Shiu, Peter (November 2007). "Euler's contribution to number theory". The Mathematical Gazette. 91 (522): 453–461. doi: 10.1017/S0025557200182099. JSTOR 40378418. S2CID 125064003.
 ^ Stillwell, John (2010). Mathematics and Its History. Undergraduate Texts in Mathematics. Springer. p. 40. ISBN 9781441960528. Archived from the original on 27 July 2021. Retrieved 6 June 2021..
 ^ Dunham 1999, Ch. 1, Ch. 4.
 ^ Caldwell, Chris. "The largest known prime by year". PrimePages. University of Tennessee at Martin. Archived from the original on 19 August 2013. Retrieved 9 June 2021.
 ^ Hopkins, Brian; Wilson, Robin (2007). "Euler's science of combinations". Leonhard Euler: Life, Work and Legacy. Stud. Hist. Philos. Math. 5. Amsterdam: Elsevier. pp. 395–408. MR 3890500.
 ^ ^{a} ^{b} Alexanderson, Gerald (July 2006). "Euler and Königsberg's bridges: a historical view". Bulletin of the American Mathematical Society. 43 (4): 567. doi: 10.1090/S027309790601130X.
 ^ ^{a} ^{b} Richeson 2012.
 ^ Gibbons, Alan (1985). Algorithmic Graph Theory. Cambridge University Press. p. 72. ISBN 9780521288811. Archived from the original on 20 August 2021. Retrieved 12 November 2015.
 ^ Cauchy, A. L. (1813). "Recherche sur les polyèdres – premier mémoire". Journal de l'École polytechnique (in French). 9 (Cahier 16): 66–86. Archived from the original on 10 June 2021. Retrieved 10 June 2021.
 ^ L'Huillier, S.A.J. (1812–1813). "Mémoire sur la polyèdrométrie". Annales de mathématiques pures et appliquées. 3: 169–89. Archived from the original on 10 June 2021. Retrieved 10 June 2021.
 ^ Butcher, John C. (2003). Numerical Methods for Ordinary Differential Equations. New York: John Wiley & Sons. p. 45. ISBN 9780471967583. Archived from the original on 19 June 2021. Retrieved 8 June 2021.
 ^ Calinger 2016, pp. 96, 137.
 ^ Ferraro 2008, pp. 171–180, Chapter 14: Euler's derivation of the Euler–Maclaurin summation formula.
 ^ Mills, Stella (1985). "The independent derivations by Leonhard Euler and Colin Maclaurin of the Euler–Maclaurin summation formula". Archive for History of Exact Sciences. 33 (1–3): 1–13. doi: 10.1007/BF00328047. MR 0795457. S2CID 122119093.
 ^ Ojalvo, Morris (December 2007). "Three hundred years of bar theory". Journal of Structural Engineering. 133 (12): 1686–1689. doi: 10.1061/(asce)07339445(2007)133:12(1686).
 ^ Youschkevitch, A. P. (1971). "Euler, Leonhard". In Gillispie, Charles Coulston (ed.). Dictionary of Scientific Biography. 4: Richard Dedekind – Firmicus Maternus. New York: Charles Scribner's Sons. pp. 467–484. ISBN 9780684169644.
 ^ ^{a} ^{b} Davidson, Michael W. (February 2011). "Pioneers in Optics: Leonhard Euler and ÉtienneLouis Malus". Microscopy Today. 19 (2): 52–54. doi: 10.1017/s1551929511000046. S2CID 122853454.
 ^ Calinger 1996, pp. 152–153.
 ^ Home, R. W. (1988). "Leonhard Euler's 'antiNewtonian' theory of light". Annals of Science. 45 (5): 521–33. doi: 10.1080/00033798800200371. MR 0962700.
 ^ Li, Shengcai (October 2015). "Tiny bubbles challenge giant turbines: Three Gorges puzzle". Interface Focus. The Royal Society. 5 (5): 20150020. doi: 10.1098/rsfs.2015.0020. PMC 4549846.
 ^ Euler, Leonhard (1757). "Principes généraux de l'état d'équilibre d'un fluide" [General principles of the state of equilibrium of a fluid]. Académie Royale des Sciences et des BellesLettres de Berlin, Mémoires (in French). 11: 217–73. Archived from the original on 6 May 2021. Retrieved 12 June 2021. Translated into English as Frisch, Uriel (2008). "Translation of Leonhard Euler's: General Principles of the Motion of Fluids". arXiv: 0802.2383 [ nlin.CD].
 ^ Gautschi 2008, p. 22.
 ^ Baron, Margaret E. (May 1969). "A note on the historical development of logic diagrams". The Mathematical Gazette. 53 (383): 113–125. doi: 10.2307/3614533. JSTOR 3614533.
 ^ Lemanski, Jens (2016). "Means or end? On the valuation of logic diagrams". LogicPhilosophical Studies. 14: 98–122.
 ^ Rodgers, Peter (June 2014). "A survey of Euler diagrams" (PDF). Journal of Visual Languages & Computing. 25 (3): 134–155. doi: 10.1016/j.jvlc.2013.08.006. Archived (PDF) from the original on 20 August 2021. Retrieved 23 July 2021.
 ^ Calinger 1996, pp. 144–45.
 ^ ^{a} ^{b} Pesic, Peter (2014). "Euler: the mathematics of musical sadness; Euler: from sound to light". Music and the Making of Modern Science. MIT Press. pp. 133–150, 151–160. ISBN 9780262027274. Archived from the original on 10 June 2021. Retrieved 10 June 2021.
 ^ Tegg, Thomas (1829). "Binary logarithms". London encyclopaedia; or, Universal dictionary of science, art, literature and practical mechanics: comprising a popular view of the present state of knowledge, Volume 4. pp. 142–143. Archived from the original on 23 May 2021. Retrieved 13 June 2021.
 ^ Euler, Leonhard (1739). Tentamen novae theoriae musicae [An attempt at a new theory of music, exposed in all clearness, according to the most wellfounded principles of harmony] (in Latin). St. Petersburg: Imperial Academy of Sciences. p. 115. Archived from the original on 12 June 2021. Retrieved 12 June 2021 – via Euler archive.
 ^ Emery, Eric (2000). Temps et musique. Lausanne: L'Âge d'homme. pp. 344–345.
 ^ Mattheson, Johannes (1731). Grosse GeneralBaßSchule. I. Hamburg. pp. 104–06. Mentioned by Euler. Also: Mattheson, Johannes (1719). Exemplarische OrganistenProbe. Hamburg. pp. 57–59.

^ See:
 Perret, Wilfrid (1926). Some Questions of Musical Theory. Cambridge: W. Heffer & Sons. pp. 60–62.
 "What is an EulerFokker genus?". Microtonality. HugensFokker Foundation. Archived from the original on 21 May 2015. Retrieved 12 June 2015.
 ^ Leonhard Euler,Tentamen novae theoriae musicae, St Petersburg, 1739, p. 147; De harmoniae veris principiis, St Petersburg, 1774, p. 350.
 ^ Gollin, Edward (2009). "Combinatorial and transformational aspects of Euler's Speculum Musicum". In Klouche, T.; Noll, Th. (eds.). Mathematics and Computation in Music: First International Conference, MCM 2007 Berlin, Germany, May 18–20, 2007, Revised Selected Papers. Communications in Computer and Information Science. 37. Springer. pp. 406–411. doi: 10.1007/9783642045790_40.
 ^ Lindley, Mark; TurnerSmith, Ronald (1993). Mathematical Models of Musical Scales. Bonn: Verlag für systematische Musikwissenschaft. pp. 234–239. See also Nolan, Catherine (2002). "Music Theory and Mathematics". In Christensen, Th. (ed.). The Cambridge History of Western Music Theory. New York: Cambridge University Press. pp. 278–279.
 ^ Bailhache, Patrice (17 January 1997). "La Musique traduite en Mathématiques: Leonhard Euler". Communication au colloque du Centre François Viète, "Problèmes de traduction au XVIIIe siècle", Nantes (in French). Archived from the original on 28 November 2015. Retrieved 12 June 2015.
 ^ Calinger 1996, p. 123.
 ^ Calinger 1996, pp. 153–54
 ^ Euler, Leonhard (1747). Rettung der Göttlichen Offenbahrung gegen die Einwürfe der Freygeister [Defense of divine revelation against the objections of the freethinkers] (in German). Berlin: Ambrosius Haude and Johann Carl Spener. Archived from the original on 12 June 2021. Retrieved 12 June 2021 – via Euler archive.
 ^ Ho, Andie. "Comparison to the last edition of Euler's Letters published by de Condorcet, with the original edition" (PDF). Article, 2011. Archived (PDF) from the original on 28 April 2015. Retrieved 26 July 2021.
 ^
^{a}
^{b} See:
 Brown, B. H. (May 1942). "The Euler–Diderot anecdote". The American Mathematical Monthly. 49 (5): 302–03. doi: 10.2307/2303096. JSTOR 2303096.
 Gillings, R. J. (February 1954). "The socalled Euler–Diderot incident". The American Mathematical Monthly. 61 (2): 77–80. doi: 10.2307/2307789. JSTOR 2307789.
 Struik, Dirk J. (1967). A Concise History of Mathematics (3rd revised ed.). Dover Books. p. 129. ISBN 9780486602554.
 ^ Marty, Jacques (1988). "Quelques aspects des travaux de Diderot en " mathématiques mixtes "" [Some aspects of Diderot's work in general mathematics]. Recherches sur Diderot et sur l'Encyclopédie (in French). 4 (1): 145–147. Archived from the original on 24 September 2015. Retrieved 20 April 2012.
 ^ "Schweizerische Nationalbank (SNB) – Sechste Banknotenserie (1976)". Swiss National Bank. Archived from the original on 3 May 2021. Retrieved 15 June 2021.
 ^ "Schweizerische Nationalbank (SNB) – Siebte Banknotenserie (1984)". Swiss National Bank. Archived from the original on 23 April 2021. Retrieved 15 June 2021.
 ^ "E" (PDF). Members of the American Academy of Arts & Sciences, 1780–2017. American Academy of Arts and Sciences. pp. 164–179. Archived (PDF) from the original on 18 February 2019. Retrieved 17 February 2019. Entry for Euler is on p. 177.
 ^ Schmadel, Lutz D., ed. (2007). "(2002) Euler". Dictionary of Minor Planet Names. Berlin, Heidelberg: Springer Publishing. p. 162. doi: 10.1007/9783540299257_2003. ISBN 9783540299257.
 ^ Fraser, Craig G. (11 February 2005). Leonhard Euler's 1744 book on the calculus of variations. ISBN 9780080457444. In GrattanGuinness 2005, pp. 168–80
 ^ Euler, Leonhard (1744). Methodus inveniendi lineas curvas maximi minimive proprietate gaudentes, sive solutio problematis isoperimetrici lattissimo sensu accepti [A method for finding curved lines enjoying properties of maximum or minimum, or solution of isoperimetric problems in the broadest accepted sense] (in Latin). Bosquet. Archived from the original on 8 June 2021. Retrieved 8 June 2021 – via Euler archive.
 ^ Reich, Karin (11 February 2005). 'Introduction' to analysis. ISBN 9780080457444. In GrattanGuinness 2005, pp. 181–90
 ^ ^{a} ^{b} ^{c} Ferraro, Giovanni (2007). "Euler's treatises on infinitesimal analysis: Introductio in analysin infinitorum, institutiones calculi differentialis, institutionum calculi integralis". In Baker, Roger (ed.). Euler Reconsidered: Tercentenary Essays. Heber City, UT: Kendrick Press. pp. 39–101. MR 2384378.

^ Reviews of Introduction to Analysis of the Infinite:
 Aiton, E. J. zbMATH. Zbl 0657.01013.CS1 maint: untitled periodical ( link)
 Shiu, P. (December 1990). The Mathematical Gazette. 74 (470): 392–393. doi: 10.2307/3618156. JSTOR 3618156.CS1 maint: untitled periodical ( link)
 Ştefănescu, Doru. Mathematical Reviews. MR 1025504.CS1 maint: untitled periodical ( link)
 ^ Demidov, S. S. (2005). Treatise on the differential calculus. ISBN 9780080457444. Archived from the original on 18 June 2021. Retrieved 12 November 2015. In GrattanGuinness 2005, pp. 191–98.
 ^ ^{a} ^{b} ^{c} Kleinert, Andreas (2015). "Leonhardi Euleri Opera omnia: Editing the works and correspondence of Leonhard Euler". Prace Komisji Historii Nauki PAU. Jagiellonian University. 14: 13–35. doi: 10.4467/23921749pkhn_pau.16.002.5258.
 ^ Euler, Leonhard; Fuss, Nikola Ivanovich; Fuss, Paul (1862). Opera postuma mathematica et physica anno 1844 detecta quae Academiae scientiarum petropolitanae obtulerunt ejusque auspicus ediderunt auctoris pronepotes Paulus Henricus Fuss et Nicolaus Fuss. Imperatorskaia akademīia nauk (Russia).
 ^ Plüss, Matthias. "Der Goethe der Mathematik". Swiss National Science Foundation. Archived from the original on 24 June 2021. Retrieved 16 June 2021.
 ^ Calinger 2016, pp. ix–x.
 ^ "The Eneström Index". Euler Archive. Archived from the original on 9 August 2021. Retrieved 27 May 2021.
 ^ Knapp, Susan (19 February 2007). "Dartmouth students build online archive of historic mathematician". Vox of Dartmouth. Dartmouth University. Archived from the original on 28 May 2010.
 ^ Klyve, Dominic (June–July 2011). "Euler Archive Moves To MAA Website". MAA FOCUS. Mathematical Association of America. Retrieved 9 January 2020.
 ^ Euler Archive Archived 7 June 2021 at the Wayback Machine, University of the Pacific
Sources
 Calinger, Ronald (1996). "Leonhard Euler: The First St. Petersburg Years (1727–1741)". Historia Mathematica. 23 (2): 121–66. doi: 10.1006/hmat.1996.0015.
 Calinger, Ronald (2016). Leonhard Euler: Mathematical Genius in the Enlightenment. Princeton University Press. ISBN 9780691119274. Archived from the original on 13 July 2017. Retrieved 4 January 2017.
 Dunham, William (1999). Euler: The Master of Us All. Dolciani Mathematical Expositions. 22. Mathematical Association of America. ISBN 9780883853283. Archived from the original on 13 June 2021. Retrieved 12 November 2015.
 Ferraro, Giovanni (2008). The Rise and Development of the Theory of Series up to the Early 1820s. ISBN 9780387734675. Archived from the original on 29 May 2021. Retrieved 27 May 2021.
 Gekker, I. R.; Euler, A. A. (2007). "Leonhard Euler's family and descendants". In Bogolyubov, Nikolaĭ Nikolaevich; Mikhaĭlov, G. K.; Yushkevich, Adolph Pavlovich (eds.). Euler and Modern Science. Translated by Robert Burns. Mathematical Association of America. ISBN 9780883855645. Archived from the original on 18 May 2016. Retrieved 12 November 2015.
 Gautschi, Walter (2008). "Leonhard Euler: His Life, the Man, and His Works". SIAM Review. 50 (1): 3–33. Bibcode: 2008SIAMR..50....3G. CiteSeerX 10.1.1.177.8766. doi: 10.1137/070702710. ISSN 00361445. JSTOR 20454060.
 GrattanGuinness, Ivor, ed. (2005). Landmark Writings in Western Mathematics 1640–1940. Elsevier. ISBN 9780080457444.
 Richeson, David S. (2012). Euler's Gem: The Polyhedron Formula and the Birth of Topology. Princeton University Press. p. 17. ISBN 9781400838561.
Further reading
 Bradley, Robert E.; D'Antonio, Lawrence A.; Sandifer, Charles Edward (2007). Euler at 300: An Appreciation. Mathematical Association of America. ISBN 9780883855652.
 Bradley, Robert E.; Sandifer, Charles Edward, eds. (2007). Leonhard Euler: Life, Work and Legacy. Studies in the History and Philosophy of Mathematics. 5. Elsevier. ISBN 9780444527288. Archived from the original on 19 June 2021. Retrieved 8 June 2021.
 Dunham, William (2007). The Genius of Euler: Reflections on his Life and Work. Mathematical Association of America. ISBN 9780883855584.
 Hascher, Xavier; Papadopoulos, Athanase, eds. (2015). Leonhard Euler : Mathématicien, physicien et théoricien de la musique (in French). Paris: CNRS Editions. ISBN 9782271083319. Archived from the original on 8 June 2021. Retrieved 8 June 2021.
 Sandifer, C. Edward (2007). The Early Mathematics of Leonhard Euler. Mathematical Association of America. ISBN 9780883855591.
 Sandifer, C. Edward (2007). How Euler Did It. Mathematical Association of America. ISBN 9780883855638.
 Sandifer, C. Edward (2015). How Euler Did Even More. Mathematical Association of America. ISBN 9780883855843. Archived from the original on 16 June 2021. Retrieved 8 June 2021.
 Schattschneider, Doris, ed. (November 1983). "A Tribute to Leonhard Euler 1707–1783 (special issue)". Mathematics Magazine. 56 (5). JSTOR i326726.
External links
 Media related to Leonhard Euler at Wikimedia Commons
 Leonhard Euler at the Mathematics Genealogy Project
 Euler Tercentenary 2007
 The Euler Society
 Euler Family Tree
 Euler's Correspondence with Frederick the Great, King of Prussia
 O'Connor, John J.; Robertson, Edmund F. "Leonhard Euler". MacTutor History of Mathematics archive. University of St Andrews.
 Works by Leonhard Euler at LibriVox (public domain audiobooks)
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