# Jackson theorem

From Encyclopedia of Mathematics

A theorem in the theory of approximation of functions which yields an estimate from above for the best approximation of a function by algebraic polynomials (for a periodic function, by trigonometric polynomials). Jackson's theorem makes it possible to study the properties of best approximations in dependence on the differentiability properties of the function. Cf. Jackson inequality.

**How to Cite This Entry:**

Jackson theorem. V.I. Berdyshev (originator),

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Jackson_theorem&oldid=15983

This text originally appeared in Encyclopedia of Mathematics - ISBN 1402006098