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Difference between revisions of "Chebyshev approximation"

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''uniform approximation''
 
''uniform approximation''
  
Approximation of a continuous function <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c021/c021830/c0218301.png" /> defined on a set <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c021/c021830/c0218302.png" /> by functions <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c021/c021830/c0218303.png" /> from a given class of functions, where the measure of approximation is the deviation in the uniform metric
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Approximation of a continuous function $f$ defined on a set $M$ by functions $S$ from a given class of functions, where the measure of approximation is the deviation in the uniform metric
  
<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c021/c021830/c0218304.png" /></td> </tr></table>
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$$\rho(f,S)=\sup_{x\in M}|f(x)-S(x)|.$$
  
P.L. Chebyshev in 1853 [[#References|[1]]] raised and studied the problem of best uniform approximation of a continuous function by algebraic polynomials of degree not exceeding <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c021/c021830/c0218305.png" />. For this problem, and also for the more general problem concerning best uniform approximation of a function by rational functions, he obtained fundamental results, and at the same time laid the foundations for the theory of [[Best approximation|best approximation]].
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P.L. Chebyshev in 1853 [[#References|[1]]] raised and studied the problem of best uniform approximation of a continuous function by algebraic polynomials of degree not exceeding $n$. For this problem, and also for the more general problem concerning best uniform approximation of a function by rational functions, he obtained fundamental results, and at the same time laid the foundations for the theory of [[Best approximation|best approximation]].
  
 
====References====
 
====References====

Latest revision as of 08:42, 19 April 2014

uniform approximation

Approximation of a continuous function $f$ defined on a set $M$ by functions $S$ from a given class of functions, where the measure of approximation is the deviation in the uniform metric

$$\rho(f,S)=\sup_{x\in M}|f(x)-S(x)|.$$

P.L. Chebyshev in 1853 [1] raised and studied the problem of best uniform approximation of a continuous function by algebraic polynomials of degree not exceeding $n$. For this problem, and also for the more general problem concerning best uniform approximation of a function by rational functions, he obtained fundamental results, and at the same time laid the foundations for the theory of best approximation.

References

[1] P.L. Chebyshev, , Collected works , 2 , Moscow-Leningrad (1947) pp. 23–51 (In Russian)
[2] R.S. Guter, L.D. Kudryavtsev, B.M. Levitan, "Elements of the theory of functions" , Moscow (1963) (In Russian)


Comments

See also [a1], especially Chapt. 3, and [a2], Section 7.6. For an obvious reason, Chebyshev approximation is also called best uniform approximation.

References

[a1] E.W. Cheney, "Introduction to approximation theory" , McGraw-Hill (1966)
[a2] P.J. Davis, "Interpolation and approximation" , Dover, reprint (1975) pp. 108–126
How to Cite This Entry:
Chebyshev approximation. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Chebyshev_approximation&oldid=12729
This article was adapted from an original article by Yu.N. Subbotin (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article