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Lists of integrals

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This article is about mostly indefinite integrals in calculus. For a list of definite integrals, seeList of definite integrals.
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Calculus
abf(t)dt=f(b)f(a){\displaystyle \int _{a}^{b}f'(t)\,dt=f(b)-f(a)}
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Integration is the basic operation inintegral calculus. Whiledifferentiation has straightforwardrules by which the derivative of a complicatedfunction can be found by differentiating its simpler component functions, integration does not, so tables of known integrals are often useful. This page lists some of the most commonantiderivatives.

Historical development of integrals

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A compilation of a list of integrals (Integraltafeln) and techniques of integral calculus was published by the German mathematicianMeier Hirsch [de] (also spelled Meyer Hirsch) in 1810.[1] These tables were republished in the United Kingdom in 1823. More extensive tables were compiled in 1858 by the Dutch mathematicianDavid Bierens de Haan for hisTables d'intégrales définies, supplemented bySupplément aux tables d'intégrales définies in ca. 1864. A new edition was published in 1867 under the titleNouvelles tables d'intégrales définies.

These tables, which contain mainly integrals of elementary functions, remained in use until the middle of the 20th century. They were then replaced by the much more extensive tables ofGradshteyn and Ryzhik. In Gradshteyn and Ryzhik, integrals originating from the book by Bierens de Haan are denoted by BI.

Not allclosed-form expressions have closed-form antiderivatives; this study forms the subject ofdifferential Galois theory, which was initially developed byJoseph Liouville in the 1830s and 1840s, leading toLiouville's theorem which classifies which expressions have closed-form antiderivatives. A simple example of a function without a closed-form antiderivative isex2, whose antiderivative is (up to constants) theerror function.

Since 1968 there is theRisch algorithm for determining indefinite integrals that can be expressed in term ofelementary functions, typically using acomputer algebra system. Integrals that cannot be expressed using elementary functions can be manipulated symbolically using general functions such as theMeijer G-function.

Lists of integrals

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More detail may be found on the following pages for thelists of integrals:

Gradshteyn,Ryzhik,Geronimus,Tseytlin, Jeffrey, Zwillinger, andMoll's (GR)Table of Integrals, Series, and Products contains a large collection of results. An even larger, multivolume table is theIntegrals and Series byPrudnikov,Brychkov, andMarichev (with volumes 1–3 listing integrals and series ofelementary andspecial functions, volume 4–5 are tables ofLaplace transforms). More compact collections can be found in e.g. Brychkov, Marichev, Prudnikov'sTables of Indefinite Integrals, or as chapters in Zwillinger'sCRC Standard Mathematical Tables and Formulae orBronshtein and Semendyayev'sGuide Book to Mathematics,Handbook of Mathematics orUsers' Guide to Mathematics, and other mathematical handbooks.

Other useful resources includeAbramowitz and Stegun and theBateman Manuscript Project. Both works contain many identities concerning specific integrals, which are organized with the most relevant topic instead of being collected into a separate table. Two volumes of the Bateman Manuscript are specific to integral transforms.

There are several web sites which have tables of integrals and integrals on demand.Wolfram Alpha can show results, and for some simpler expressions, also the intermediate steps of the integration.Wolfram Research also operates another online service, the Mathematica Online Integrator.

Integrals of simple functions

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C is used for anarbitrary constant of integration that can only be determined if something about the value of the integral at some point is known. Thus, each function has an infinite number ofantiderivatives.

These formulas only state in another form the assertions in thetable of derivatives.

Integrals with a singularity

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When there is asingularity in the function being integrated such that the antiderivative becomes undefined at some point (the singularity), thenC does not need to be the same on both sides of the singularity. The forms below normally assume theCauchy principal value around a singularity in the value ofC, but this is not necessary in general. For instance, in1xdx=ln|x|+C{\displaystyle \int {1 \over x}\,dx=\ln \left|x\right|+C}there is a singularity at 0 and theantiderivative becomes infinite there. If the integral above were to be used to compute a definite integral between −1 and 1, one would get the wrong answer 0. This however is the Cauchy principal value of the integral around the singularity. If the integration is done in the complex plane the result depends on the path around the origin, in this case the singularity contributes −iπ when using a path above the origin andiπ for a path below the origin. A function on the real line could use a completely different value ofC on either side of the origin as in:[2]1xdx=ln|x|+{Aif x>0;Bif x<0.{\displaystyle \int {1 \over x}\,dx=\ln |x|+{\begin{cases}A&{\text{if }}x>0;\\B&{\text{if }}x<0.\end{cases}}}

Rational functions

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See also:List of integrals of rational functions

The following function has a non-integrable singularity at 0 forn ≤ −1:

Exponential functions

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See also:List of integrals of exponential functions

Logarithms

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See also:List of integrals of logarithmic functions

Trigonometric functions

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See also:List of integrals of trigonometric functions

Inverse trigonometric functions

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See also:List of integrals of inverse trigonometric functions

Hyperbolic functions

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See also:List of integrals of hyperbolic functions

Inverse hyperbolic functions

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See also:List of integrals of inverse hyperbolic functions

Products of functions proportional to their second derivatives

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Absolute-value functions

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Letf be acontinuous function, that has at most onezero. Iff has a zero, letg be the unique antiderivative off that is zero at the root off; otherwise, letg be any antiderivative off. Then|f(x)|dx=sgn(f(x))g(x)+C,{\displaystyle \int \left|f(x)\right|\,dx=\operatorname {sgn}(f(x))g(x)+C,}wheresgn(x) is thesign function, which takes the values −1, 0, 1 whenx is respectively negative, zero or positive.

This can be proved by computing the derivative of the right-hand side of the formula, taking into account that the condition ong is here for insuring the continuity of the integral.

This gives the following formulas (wherea ≠ 0), which are valid over any interval wheref is continuous (over larger intervals, the constantC must be replaced by apiecewise constant function):

If the functionf does not have any continuous antiderivative which takes the value zero at the zeros off (this is the case for the sine and the cosine functions), thensgn(f(x)) ∫f(x)dx is an antiderivative off on everyinterval on whichf is not zero, but may be discontinuous at the points wheref(x) = 0. For having a continuous antiderivative, one has thus to add a well chosenstep function. If we also use the fact that the absolute values of sine and cosine are periodic with periodπ, then we get:

Special functions

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Ci,Si:Trigonometric integrals,Ei:Exponential integral,li:Logarithmic integral function,erf:Error function

Definite integrals lacking closed-form antiderivatives

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See also:List of definite integrals

There are some functions whose antiderivativescannot be expressed inclosed form. However, the values of the definite integrals of some of these functions over some common intervals can be calculated. A few useful integrals are given below.

If the functionf hasbounded variation on the interval[a,b], then themethod of exhaustion provides a formula for the integral:abf(x)dx=(ba)n=1m=12n1(1)m+12nf(a+m(ba)2n).{\displaystyle \int _{a}^{b}{f(x)\,dx}=(b-a)\sum \limits _{n=1}^{\infty }{\sum \limits _{m=1}^{2^{n}-1}{\left({-1}\right)^{m+1}}}2^{-n}f(a+m\left({b-a}\right)2^{-n}).}

The "sophomore's dream":01xxdx=n=1nn(=1.29128599706266)01xxdx=n=1(n)n(=0.78343051071213){\displaystyle {\begin{aligned}\int _{0}^{1}x^{-x}\,dx&=\sum _{n=1}^{\infty }n^{-n}&&(=1.29128\,59970\,6266\dots )\\[6pt]\int _{0}^{1}x^{x}\,dx&=-\sum _{n=1}^{\infty }(-n)^{-n}&&(=0.78343\,05107\,1213\dots )\end{aligned}}}attributed toJohann Bernoulli.

See also

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References

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  1. ^Hirsch, Meyer (1810).Integraltafeln: oder, Sammlung von integralformeln (in German). Duncker & Humblot.
  2. ^Serge Lang .A First Course in Calculus, 5th edition, p. 290
  3. ^"Reader Survey: log|x| +C", Tom Leinster,Then-category Café, March 19, 2012

Further reading

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External links

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Tables of integrals

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Derivations

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Online service

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Open source programs

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