arithmetic–geometric mean identities

E157393

Arithmetic–geometric mean identities are a collection of formulas and relationships that express various mathematical constants and special functions in terms of the arithmetic–geometric mean of two numbers.

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Predicate Object
instanceOf mathematical identity collection
result in analysis
special function identity
field mathematical analysis
number theory
special functions
hasKeyFormula K(1/\sqrt{2}) = \frac{\Gamma(1/4)^{2}}{4\sqrt{\pi}}
K(k) = \frac{\pi}{2\,\operatorname{AGM}(1,\sqrt{1-k^{2}})}
\frac{1}{\operatorname{AGM}(1,\sqrt{1-k^{2}})} = \frac{2}{\pi}K(k)
\int_{0}^{\infty}\frac{dx}{\sqrt{(x^{2}+a^{2})(x^{2}+b^{2})}} = \frac{\pi}{2\,\operatorname{AGM}(a,b)}
\int_{0}^{\pi/2}\frac{d\theta}{\sqrt{a^{2}\cos^{2}\theta + b^{2}\sin^{2}\theta}} = \frac{\pi}{2\,\operatorname{AGM}(a,b)}
\operatorname{AGM}(1,1/\sqrt{2}) = \frac{\Gamma(1/4)^{2}}{4\sqrt{\pi^{3}}}
\operatorname{AGM}(1,\sqrt{1-k^{2}}) = \frac{\pi}{4}\,\frac{1}{K(k)}
\operatorname{AGM}(1,\sqrt{1-k^{2}})\,\operatorname{AGM}(1,\sqrt{1-k'^{2}}) = \frac{\pi}{2} with k'^{2}=1-k^{2}
\operatorname{AGM}(a,b) = \frac{\pi}{4}\,\frac{a}{K(k)} with k^{2}=1-\left(\frac{b}{a}\right)^{2},\ a\ge b>0
\pi = 2\,\operatorname{AGM}(1,1/\sqrt{2})^{2}\,\sum_{n=0}^{\infty}2^{n}(a_{n}^{2}-b_{n}^{2}) (Gauss–Legendre type)
\pi = 2\,\operatorname{AGM}(1,\sqrt{1-k^{2}})\,K(k)
hasProperty connect arithmetic means, geometric means, and elliptic integrals
express many special values of elliptic integrals in closed form
provide rapidly convergent algorithms for computing elliptic integrals
provide rapidly convergent algorithms for computing pi
historicalOrigin 19th century theory of elliptic integrals
work of Carl Friedrich Gauss on the arithmetic–geometric mean
relatedConcept Borwein brothers’ AGM-based pi algorithms
Gauss transformation for elliptic integrals
arithmetic–geometric mean identities self-linksurface differs
surface form: Gauss–Legendre algorithm

Jacobi theta functions
Landen transformations
Ramanujan-type series for 1/\pi
modular invariants
relatesQuantity Gamma function at rational arguments
arithmetic–geometric mean of two positive numbers
complete elliptic integral K(k)
complete elliptic integrals of the second kind
integrals of rational functions of trigonometric functions
modulus k of an elliptic integral
usedFor derivation of modular equations
evaluation of special functions
fast algorithms for pi such as Gauss–Legendre algorithm
high-precision computation of mathematical constants
usesConcept Beta function
Gamma function
arithmetic–geometric mean
complete elliptic integral of the first kind
elliptic functions
elliptic integrals
modular functions
pi
theta functions

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Referenced by (4)

Full triples — surface form annotated when it differs from this entity's canonical label.

Gauss’s constant appearsIn arithmetic–geometric mean identities
Gauss’s constant definedVia arithmetic–geometric mean identities
this entity surface form: arithmetic–geometric mean
Gauss’s constant relatedTo arithmetic–geometric mean identities
this entity surface form: Gaussian arithmetic–geometric mean
arithmetic–geometric mean identities relatedConcept arithmetic–geometric mean identities self-linksurface differs
this entity surface form: Gauss–Legendre algorithm