On the stability of a class of cosine type functional equations

Abstract

The aim of this paper is to investigate the stability problem for the pexiderized trigonometric functional equationwhere G is an arbitrary group, f 1 , f 2 , g 1 and g 2 are complex valued functions on G and σ is an involution of G. Results of this paper also can be extended to the setting of monoids (that is, a semigroup with identity) that need not be abelian.