The mathematical constant e is the unique real number such that the function ex has the same value as the slope of the tangent line, for all values of x. A mathematical constant is a number usually a Real number, that arises naturally in Mathematics. In Mathematics, the real numbers may be described informally in several different ways In Calculus, a branch of mathematics the derivative is a measurement of how a function changes when the values of its inputs change [1] More generally, the only functions equal to their own derivatives are of the form Cex, where C is a constant. In Calculus, a branch of mathematics the derivative is a measurement of how a function changes when the values of its inputs change [2] The function ex so defined is called the exponential function, and its inverse is the natural logarithm, or logarithm to base e. The exponential function is a function in Mathematics. The application of this function to a value x is written as exp( x) In Mathematics, if &fnof is a function from A to B then an inverse function for &fnof is a function in the opposite direction from B The natural logarithm, formerly known as the Hyperbolic logarithm is the Logarithm to the base e, where e is an irrational radix|basis (topologyIn Arithmetic, the base refers to the number b in an expression of the form b n. The number e is also commonly defined as the base of the natural logarithm (using an integral to define the latter), as the limit of a certain sequence, or as the sum of a certain series (see representations of e, below). The European Space Agency 's INTErnational Gamma-Ray Astrophysics Laboratory ( INTEGRAL) is detecting some of the most energetic radiation that comes from space The limit of a sequence is one of the oldest concepts in Mathematical analysis. In Mathematics, a sequence is an ordered list of objects (or events In Mathematics, a series is often represented as the sum of a Sequence of terms That is a series is represented as a list of numbers with
The number e is one of the most important numbers in mathematics,[3] alongside the additive and multiplicative identities 0 and 1, the constant π, and the imaginary unit i. Mathematics For any number x: x ·1 = 1· x = x (1 is the multiplicative identity IMPORTANT NOTICE Please note that Wikipedia is not a database to store the millions of digits of π please refrain from adding those to Wikipedia as it could cause technical problems Definition By definition the imaginary unit i is one solution (of two of the Quadratic equation
The number e is sometimes called Euler's number after the Swiss mathematician Leonhard Euler. Switzerland (English pronunciation; Schweiz Swiss German: Schwyz or Schwiiz Suisse Svizzera Svizra officially the Swiss Confederation A mathematician is a person whose primary area of study and research is the field of Mathematics. (e is not to be confused with γ – the Euler–Mascheroni constant, sometimes called simply Euler's constant. The Euler–Mascheroni constant (also called the Euler constant) is a Mathematical constant recurring in analysis and Number theory, usually )
Since e is transcendental, and therefore irrational, its value cannot be given exactly as a finite or eventually repeating decimal. In Mathematics, a transcendental number is a Complex number that is not algebraic, that is not a solution of a non-zero Polynomial equation In Mathematics, an irrational number is any Real number that is not a Rational number — that is it is a number which cannot be expressed as a fraction The numerical value of e truncated to 20 decimal places is:
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The first references to the constant were published in 1618 in the table of an appendix of a work on logarithms by John Napier. The natural logarithm, formerly known as the Hyperbolic logarithm is the Logarithm to the base e, where e is an irrational Compound interest is the concept of adding accumulated Interest back to the principal so that interest is earned on interest from that moment on In Mathematical analysis, Euler's identity, named after Leonhard Euler, is the equation e^{i \pi} + 1 = 0 \\! where This article is about Euler's formula in Complex analysis. For Euler's formula in algebraic topology and polyhedral combinatorics see Euler characteristic Half-Life (computer-game page here It's already listed in the disambiguation page Exponential growth (including Exponential decay) occurs when the growth rate of a mathematical function is proportional to the function's current value A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value In Mathematics, the series representation of Euler's number e e = \sum_{n = 0}^{\infty} \frac{1}{n!}\! can be used to prove The Mathematical constant ''e'' can be represented in a variety of ways as a Real number. In Mathematics, the Lindemann–Weierstrass theorem is a result that is very useful in establishing the transcendence of numbers For other people with the same name see John Napier (disambiguation. In Mathematics, specifically Transcendence theory, Schanuel's conjecture is the following statement Given any n Complex numbers For other people with the same name see John Napier (disambiguation. [4] However, this did not contain the constant itself, but simply a list of natural logarithms calculated from the constant. It is assumed that the table was written by William Oughtred. William Oughtred ( March 5, 1575 – June 30, 1660) was an English Mathematician. The "discovery" of the constant itself is credited to Jacob Bernoulli, who attempted to find the value of the following expression (which is in fact e):

The first known use of the constant, represented by the letter b, was in correspondence from Gottfried Leibniz to Christiaan Huygens in 1690 and 1691. For other family members named Jacob see Bernoulli family. Jacob Bernoulli (also known as James or Jacques) ( Basel Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch Leonhard Euler started to use the letter e for the constant in 1727, and the first use of e in a publication was Euler's Mechanica (1736). While in the subsequent years some researchers used the letter c, e was more common and eventually became the standard.
The exact reasons for the use of the letter e are unknown, but it may be because it is the first letter of the word exponential. Another possibility is that Euler used it because it was the first vowel after a, which he was already using for another number, but his reason for using vowels is unknown. In Phonetics, a vowel is a Sound in spoken Language, such as English ah! or oh!, pronounced with an open Vocal tract It is unlikely that Euler chose the letter because it is the first letter of his surname, since he was a very modest man and tried to give proper credit to the work of others.
Jacob Bernoulli discovered this constant by studying a question about compound interest. For other family members named Jacob see Bernoulli family. Jacob Bernoulli (also known as James or Jacques) ( Basel Compound interest is the concept of adding accumulated Interest back to the principal so that interest is earned on interest from that moment on
One simple example is an account that starts with $1. 00 and pays 100% interest per year. If the interest is credited once, at the end of the year, the value is $2. 00; but if the interest is computed and added twice in the year, the $1 is multiplied by 1. 5 twice, yielding $1. 00×1. 5² = $2. 25. Compounding quarterly yields $1. 00×1. 254 = $2. 4414…, and compounding monthly yields $1. 00×(1. 0833…)12 = $2. 613035….
Bernoulli noticed that this sequence approaches a limit (the force of interest) for more and smaller compounding intervals. Compound interest is the concept of adding accumulated Interest back to the principal so that interest is earned on interest from that moment on Compounding weekly yields $2. 692597…, while compounding daily yields $2. 714567…, just two cents more. Using n as the number of compounding intervals, with interest of 1⁄n in each interval, the limit for large n is the number that came to be known as e; with continuous compounding, the account value will reach $2. 7182818…. More generally, an account that starts at $1, and yields (1+R) dollars at simple interest, will yield eR dollars with continuous compounding.
The number e itself also has applications to probability theory, where it arises in a way not obviously related to exponential growth. Probability theory is the branch of Mathematics concerned with analysis of random phenomena Suppose that a gambler plays a slot machine that pays out with a probability of one in n and plays it n times. Then, for large n (such as a million) the probability that the gambler will win nothing at all is (approximately) 1⁄e. Probability is the likelihood or chance that something is the case or will happen
This is an example of a Bernoulli trials process. In the theory of Probability and Statistics, a Bernoulli trial is an experiment whose outcome is random and can be either of two possible outcomes "success" Each time the gambler plays the slots, there is a one in one million chance of winning. Playing one million times is modelled by the binomial distribution, which is closely related to the binomial theorem. WikipediaWikiProject Probability#Standards for a discussion of standards used for probability distribution articles such as this one In Mathematics, the binomial theorem is an important Formula giving the expansion of powers of Sums Its simplest version says The probability of winning k times out of a million trials is;

In particular, the probability of winning zero times (k=0) is

This is very close to the following limit for 1⁄e:

Another application of e, also discovered in part by Jacob Bernoulli along with Pierre Raymond de Montmort is in the problem of derangements, also known as the hat check problem. Pierre Raymond de Montmort, a French Mathematician, was born in Paris on 27 October 1678, and died there on 7 October In combinatorial Mathematics, a derangement is a Permutation in which none of the elements of the set appear in their original positions [5] Here n guests are invited to a party, and at the door each guest checks his hat with the butler who then places them into labeled boxes. But the butler does not know the name of the guests, and so must put them into boxes selected at random. The problem of de Montmort is: what is the probability that none of the hats gets put into the right box. The answer is:

As the number n of guests tends to infinity, pn approaches 1⁄e. Furthermore, the number of ways the hats can be placed into the boxes so that none of the hats is in the right box is exactly n!⁄e, rounded to the nearest integer. [6]
The number e occurs naturally in connection with many problems involving asymptotics. In pure and Applied mathematics, particularly the Analysis of algorithms, real analysis and engineering asymptotic analysis is a method of describing A prominent example is Stirling's formula for the asymptotics of the factorial function, in which both the numbers e and π enter:

A particular consequence of this is
![e = \lim_{n\to\infty} \frac{n}{\sqrt[n]{n!}}.](../../../../math/9/c/6/9c678d256067a90ef02d482bac3daa8f.png)
The principal motivation for introducing the number e, particularly in calculus, is to perform differential and integral calculus with exponential functions and logarithms. In Mathematics, Stirling's approximation (or Stirling's formula) is an approximation for large Factorials It is named in honour of James Stirling Definition The factorial function is formally defined by n!=\prod_{k=1}^n k IMPORTANT NOTICE Please note that Wikipedia is not a database to store the millions of digits of π please refrain from adding those to Wikipedia as it could cause technical problems Calculus ( Latin, calculus, a small stone used for counting is a branch of Mathematics that includes the study of limits, Derivatives In Calculus, a branch of mathematics the derivative is a measurement of how a function changes when the values of its inputs change The European Space Agency 's INTErnational Gamma-Ray Astrophysics Laboratory ( INTEGRAL) is detecting some of the most energetic radiation that comes from space The exponential function is a function in Mathematics. The application of this function to a value x is written as exp( x) In Mathematics, the logarithm of a number to a given base is the power or Exponent to which the base must be raised in order to produce [7] A general exponential function y=ax has derivative given as the limit:

The limit on the right-hand side is independent of the variable x: it depends only on the base a. In Mathematics, the limit of a function is a fundamental concept in Calculus and analysis concerning the behavior of that function near a particular When the base is e, this limit is equal to one, and so e is symbolically defined by the equation:

Consequently, the exponential function with base e is particularly suited to doing calculus. Choosing e, as opposed to some other number, as the base of the exponential function makes calculations involving the derivative much simpler.
Another motivation comes from considering the base-a logarithm. In Mathematics, the logarithm of a number to a given base is the power or Exponent to which the base must be raised in order to produce [8] Considering the definition of the derivative of logax as the limit:

Once again, there is an undetermined limit which depends only on the base a, and if that base is e, the limit is one. So symbolically,

The logarithm in this special base is called the natural logarithm (often represented as "ln"), and it also behaves well under differentiation since there is no undetermined limit to carry through the calculations. The natural logarithm, formerly known as the Hyperbolic logarithm is the Logarithm to the base e, where e is an irrational
There are thus two ways in which to select a special number a=e. One way is to set the derivative of the exponential function ax to ax. The other way is to set the derivative of the base a logarithm to 1/x. In each case, one arrives at a convenient choice of base for doing calculus. In fact, these two bases are actually the same, the number e.
Other characterizations of e are also possible: one is as the limit of a sequence, another is as the sum of an infinite series, and still others rely on integral calculus. The Mathematical constant ''e'' can be represented in a variety of ways as a Real number. The limit of a sequence is one of the oldest concepts in Mathematical analysis. In Mathematics, a series is often represented as the sum of a Sequence of terms That is a series is represented as a list of numbers with The European Space Agency 's INTErnational Gamma-Ray Astrophysics Laboratory ( INTEGRAL) is detecting some of the most energetic radiation that comes from space So far, the following two (equivalent) properties have been introduced:
1. The number e is the unique positive real number such that

2. In Mathematics, the real numbers may be described informally in several different ways The number e is the unique positive real number such that

The following three characterizations can be proven equivalent:
3. In Mathematics, the Exponential function can be characterized in many ways The number e is the limit

4. The number e is the sum of the infinite series

where n! is the factorial of n. In Mathematics, a series is often represented as the sum of a Sequence of terms That is a series is represented as a list of numbers with Definition The factorial function is formally defined by n!=\prod_{k=1}^n k
5. The number e is the unique positive real number such that
. As in the motivation, the exponential function f(x) = ex is important in part because it is the unique nontrivial function (up to multiplication by a constant) which is its own derivative

and therefore its own antiderivative as well:



The number x=e is where the global maximum occurs for the function:

More generally,
is where the global maximum occurs for the function

The infinite tetration

converges only if
due to a theorem of Leonhard Euler. The exponential function is a function in Mathematics. The application of this function to a value x is written as exp( x) In Calculus, a branch of mathematics the derivative is a measurement of how a function changes when the values of its inputs change In Calculus, an antiderivative, primitive or indefinite integral of a function f is a function F whose Derivative In Mathematics, maxima and minima, known collectively as extrema, are the largest value (maximum or smallest value (minimum that In Mathematics, tetration (also known as hyper -4
Finally, the exponential function ex is usually defined as

The real number e is irrational (see proof that e is irrational), and furthermore is transcendental (Lindemann–Weierstrass theorem). The exponential function is a function in Mathematics. The application of this function to a value x is written as exp( x) In Mathematics, an irrational number is any Real number that is not a Rational number — that is it is a number which cannot be expressed as a fraction In Mathematics, the series representation of Euler's number e e = \sum_{n = 0}^{\infty} \frac{1}{n!}\! can be used to prove In Mathematics, a transcendental number is a Complex number that is not algebraic, that is not a solution of a non-zero Polynomial equation In Mathematics, the Lindemann–Weierstrass theorem is a result that is very useful in establishing the transcendence of numbers It was the first number to be proved transcendental without having been specifically constructed for this purpose (compare with Liouville number). In Number theory, a Liouville number is a Real number x with the property that for any positive Integer n, there exist integers The proof was given by Charles Hermite in 1873. Charles Hermite (ʃaʁl ɛʁˈmit ( December 24, 1822 &ndash January 14, 1901) was a French Mathematician who did It is conjectured to be normal. A different topic is treated in the article titled Normal number (computing.
It features in Euler's formula, an important formula related to complex numbers:

The special case with x = π is known as Euler's identity:

Consequently,

from which it follows that, in the principal branch of the logarithm,

Furthermore, using the laws for exponentiation,

which is de Moivre's formula. This article is about Euler's formula in Complex analysis. For Euler's formula in algebraic topology and polyhedral combinatorics see Euler characteristic Complex plane In Mathematics, the complex numbers are an extension of the Real numbers obtained by adjoining an Imaginary unit, denoted In Mathematical analysis, Euler's identity, named after Leonhard Euler, is the equation e^{i \pi} + 1 = 0 \\! where In Mathematics, a principal branch is a function which selects one branch or "slice" of a Multi-valued function. De Moivre's formula, named after Abraham de Moivre, states that for any Complex number (and in particular for any Real number) x and any
The case,

is commonly referred to as Cis(x).
The number e can be represented as a real number in a variety of ways: as an infinite series, an infinite product, a continued fraction, or a limit of a sequence. The Mathematical constant ''e'' can be represented in a variety of ways as a Real number. In Mathematics, the real numbers may be described informally in several different ways In Mathematics, a series is often represented as the sum of a Sequence of terms That is a series is represented as a list of numbers with In Mathematics, for a Sequence of numbers a 1 a 2 a 3. the infinite product In Mathematics, a continued fraction is an expression such as x = a_0 + \cfrac{1}{a_1 + \cfrac{1}{a_2 + \cfrac{1}{a_3 + \cfrac{1}{\ddots\}}}} The limit of a sequence is one of the oldest concepts in Mathematical analysis. The chief among these representations, particularly in introductory calculus courses is the limit

given above, as well as the series

given by evaluating the above power series for ex at x=1. Calculus ( Latin, calculus, a small stone used for counting is a branch of Mathematics that includes the study of limits, Derivatives
Still other less common representations are also available. For instance, e can be represented as an infinite simple continued fraction:

Or, in a more compact form (sequence A003417 in OEIS):
![e = [[2; 1, \textbf{2}, 1, 1, \textbf{4}, 1, 1, \textbf{6}, 1, 1, \textbf{8}, 1, \ldots,1, \textbf{2n}, 1,\ldots]] \,](../../../../math/8/1/7/8176f3d48072ae8ab3b5a17b8debf226.png)
Which can be written more harmoniously by allowing zero:[9]
![e = [[ 1 , \textbf{0} , 1 , 1, \textbf{2}, 1, 1, \textbf{4}, 1 , 1 , \textbf{6}, 1, \ldots]] \,](../../../../math/7/a/5/7a58bf400066753c04aa36c645a49c6b.png)
Many other series, sequence, continued fraction, and infinite product representations of e have also been developed. In Mathematics, a continued fraction is an expression such as x = a_0 + \cfrac{1}{a_1 + \cfrac{1}{a_2 + \cfrac{1}{a_3 + \cfrac{1}{\ddots\}}}} The On-Line Encyclopedia of Integer Sequences ( OEIS) also cited simply as Sloane's, is an extensive searchable Database of Integer sequences
In addition to the deterministic analytical expressions for representation of e, as described above, there are some stochastic protocols for estimation of e. In one such protocol, random samples X1,X2,. . . ,Xn of size n from the uniform distribution on (0, 1) are used to approximate e. If

then the expectation of U is e: E(U) = e. [10][11] Thus sample averages of U variables will approximate e.
The number of known digits of e has increased dramatically during the last decades. This is due both to the increase of performance of computers as well as to algorithmic improvements. [12][13]
| Date | Decimal digits | Computation performed by |
|---|---|---|
| 1748 | 18[14] | Leonhard Euler |
| 1853 | 137 | William Shanks |
| 1871 | 205 | William Shanks |
| 1884 | 346 | J. William Shanks ( January 25, 1812 &ndash summer 1882 Houghton-le-Spring, Durham, England) was a British Amateur William Shanks ( January 25, 1812 &ndash summer 1882 Houghton-le-Spring, Durham, England) was a British Amateur M. Boorman |
| 1946 | 808 | ? |
| 1949 | 2,010 | John von Neumann (on the ENIAC) |
| 1961 | 100,265 | Daniel Shanks & John W. ENIAC, short for Electronic Numerical Integrator And Computer, was the first general-purpose electronic Computer. Wrench |
| 1994 | 10,000,000 | Robert Nemiroff & Jerry Bonnell |
| May 1997 | 18,199,978 | Patrick Demichel |
| August 1997 | 20,000,000 | Birger Seifert |
| September 1997 | 50,000,817 | Patrick Demichel |
| February 1999 | 200,000,579 | Sebastian Wedeniwski |
| October 1999 | 869,894,101 | Sebastian Wedeniwski |
| November 21, 1999 | 1,250,000,000 | Xavier Gourdon |
| July 10, 2000 | 2,147,483,648 | Shigeru Kondo & Xavier Gourdon |
| July 16, 2000 | 3,221,225,472 | Colin Martin & Xavier Gourdon |
| August 2, 2000 | 6,442,450,944 | Shigeru Kondo & Xavier Gourdon |
| August 16, 2000 | 12,884,901,000 | Shigeru Kondo & Xavier Gourdon |
| August 21, 2003 | 25,100,000,000 | Shigeru Kondo & Xavier Gourdon |
| September 18, 2003 | 50,100,000,000 | Shigeru Kondo & Xavier Gourdon |
| April 27, 2007 | 100,000,000,000 | Shigeru Kondo & Steve Pagliarulo |
In contemporary internet culture, individuals and organizations frequently pay homage to the number e. Events 164 BC - Judas Maccabaeus, son of Mattathias of the Hasmonean family restores the Temple in Jerusalem. Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Events 48 BC - Battle of Dyrrhachium, Julius Caesar barely avoids a catastrophic defeat to Pompey in Macedonia. 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Events 622 - The beginning of the Islamic calendar. 1054 - Three Roman legates fractured relations between the Western and 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Events 338 BC - A Macedonian army led by Philip II defeated the combined forces of Athens and Thebes in the 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Events 1384 - The Hongwu Emperor of Ming China, Emperor Dong hears a case of a couple who tore paper money bills while fighting 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Events 1192 - Minamoto Yoritomo becomes Seii Tai Shōgun and the De facto ruler of Japan. Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. Events 96 - Nerva is proclaimed Roman Emperor after Domitian is assassinated Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. Events 1124 - David I becomes King of Scotland. 1296 - Battle of Dunbar: The Scots are defeated Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Cyberculture is the Culture that has emerged or is emerging from the use of Computer networks for communication, entertainment and business
For example, in the IPO filing for Google, in 2004, rather than a typical round-number amount of money, the company announced its intention to raise $2,718,281,828, which is e billion dollars to the nearest dollar. Initial public offering (IPO, also referred to simply as a "public offering" is when a company issues Common stock or shares to the public for the first Google Inc is an American public corporation, earning revenue from advertising related to its Internet search, e-mail, online The United States dollar ( sign: $; code: USD) is the unit of Currency of the United States; it has also been Google was also responsible for a mysterious billboard[15] that appeared in the heart of Silicon Valley, and later in Cambridge, Massachusetts; Seattle, Washington; and Austin, Texas. For the valley nicknamed "Silicone Valley" see San Fernando Valley. Cambridge Massachusetts is a City in the Greater Boston area of Massachusetts, United States. It read {first 10-digit prime found in consecutive digits of e}. com (now defunct). Solving this problem and visiting the advertised web site led to an even more difficult problem to solve, which in turn leads to Google Labs where the visitor is invited to submit a resume. Google Labs is a website demonstrating new Google projects "that aren't quite ready for prime time" [16] The first 10-digit prime in e is 7427466391, which starts at the 99th digit. [17] (A random stream of digits has a 98. 4% chance of starting a 10-digit prime sooner. )
In another instance, the eminent computer scientist Donald Knuth let the version numbers of his program METAFONT approach e. A computer scientist is a person that has acquired knowledge of Computer science, the study of the theoretical foundations of information and computation and their application Donald Ervin Knuth (kəˈnuːθ (born 10 January 1938) is a renowned computer scientist and Professor Emeritus of the Art of Computer Metafont is a Programming language used to define vector fonts. The versions are 2, 2. 7, 2. 71, 2. 718, and so forth.