Weierstrass approximation theorem

E110605

The Weierstrass approximation theorem is a fundamental result in real analysis stating that any continuous function on a closed interval can be uniformly approximated by polynomials.

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Statements (41)

Predicate Object
instanceOf approximation theorem
theorem in real analysis
alternativeProofMethod Bernstein polynomials
convolution with approximate identities
appliesTo real-valued continuous functions on compact subsets of R (via reduction to intervals)
approximationFamily polynomials with real coefficients
approximationType uniform approximation
assumption interval is compact in R
category density result
existence theorem
codomainCondition real-valued function
conclusion there exists a polynomial whose uniform distance to the function is less than epsilon
consequence continuous functions on [a,b] can be approximated arbitrarily well by elementary functions (polynomials)
doesNotRequire differentiability of the function
periodicity of the function
domainCondition domain is a closed interval [a,b] in R
function is continuous
field approximation theory
real analysis
generalizationOf Stone–Weierstrass theorem
historicalYear 1885
implies polynomials are dense in C([a,b]) with respect to the uniform norm
inspired development of abstract approximation theory
isFundamentalResultIn approximation theory curriculum
undergraduate real analysis
namedAfter Karl Weierstrass
norm supremum norm
originalProofMethod trigonometric polynomials and substitution
quantifier for every continuous function on [a,b]
for every epsilon greater than 0
relatedTo Bernstein polynomials
Fourier analysis
surface form: Fourier series

Runge approximation theorem
Stone–Weierstrass theorem
space C([a,b])
statement Every continuous real-valued function on a closed and bounded interval can be uniformly approximated by polynomials.
topologicalStatement polynomials are dense in the space of continuous functions on a compact interval
usedIn construction of polynomial interpolants
functional analysis
numerical analysis
theory of function approximation

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

Karl Weierstrass notableFor Weierstrass approximation theorem
Whitney approximation theorem relatedTo Weierstrass approximation theorem
this entity surface form: Stone–Weierstrass theorem
Whitney approximation theorem relatedTo Weierstrass approximation theorem
Whitney approximation theorem classification Weierstrass approximation theorem
this entity surface form: approximation theorem