Estimates of approximation of elements of Hilbert space by subspaces spanned by given unit expansion

V.F. Babenko (Oles Honchar Dnipropetrovsk National University),
S.V. Savela (Oles Honchar Dnipropetrovsk National University)


The exact inequalities of the Jackson-Chernih type of the approximation in the Hilbert space are obtained.


best approximation; exact inequalities; Hilbert space; expansion unit; group unitary operators


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ISSN (Online): 2664-5009
ISSN (Print): 2664-4991