The main result of the paper estimates the asymptotic behavior of local polynomial approximation for functions at a point via the behavior of μ-differences, a generalization of the kth difference. The result is applied to prove several new and extend classical results on pointwise differentiability of functions including Marcinkiewicz-Zygmund’s and M. Weiss’ theorems. In particular, we present a solution of the problem posed in the 30s by Marcinkiewicz and Zygmund.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-sm214-2-5, author = {Yu. A. Brudnyi and I. E. Gopengauz}, title = {Whitney type inequality, pointwise version}, journal = {Studia Mathematica}, volume = {215}, year = {2013}, pages = {167-194}, zbl = {06155480}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-sm214-2-5} }
Yu. A. Brudnyi; I. E. Gopengauz. Whitney type inequality, pointwise version. Studia Mathematica, Tome 215 (2013) pp. 167-194. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-sm214-2-5/