Richard’s inequality, Cauchy–Schwarz’s inequality, and approximate solutions of Sincov’s equation

Fechner, Włodzimierz

doi:10.1090/proc/14543

Richard’s inequality, Cauchy–Schwarz’s inequality, and approximate solutions of Sincov’s equation
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Proc. Amer. Math. Soc. 147 (2019), 3955-3960 Request permission

Abstract:

We observe a connection between Cauchy–Schwarz’s and Richard’s inequalities in inner product spaces and a Ulam-type stability problem for the multiplicative Sincov functional equation. We prove that this equation is superstable for unbounded mappings, i.e., every unbounded approximate solution is an exact solution.

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