Bulletin of the
Korean Mathematical Society
BKMS

ISSN(Print) 1015-8634 ISSN(Online) 2234-3016

Article

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Bull. Korean Math. Soc. 2009; 46(2): 235-243

Printed March 1, 2009

https://doi.org/10.4134/BKMS.2009.46.2.235

Copyright © The Korean Mathematical Society.

Notes on the superstability of d'Alembert type functional equations

Peng Cao and Bing Xu

Sichuan University

Abstract

In this paper we will investigate the superstability of the generalized d'Alembert type functional equations $\sum_{i=1}^{m}f(x+\sigma^{i}(y))=kg(x)f(y)$ and $\sum_{i=1}^{m}f(x+\sigma^{i}(y))=kf(x)g(y)$.

Keywords: d'Alembert functional equation, superstability, cosine function

MSC numbers: 39B82, 39B32