The aim of this paper is to investigate the stability problem for the pexiderized trigonometric functional equation f₁(xy)+f₂(xσ(y))=2g₁(x)g₂(y), x,y∈G, where G is an arbitrary group, f₁,f₂,g₁ and g₂ 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.
@article{29563,
title = {On the stability of a class of cosine type functional equations},
journal = {Boletim da Sociedade Paranaense de Matem\'atica},
volume = {37},
year = {2017},
doi = {10.5269/bspm.v37i2.29563},
language = {EN},
url = {http://dml.mathdoc.fr/item/29563}
}
Rassias, John Michael; Zeglami, Driss; Charifi, Ahmed. On the stability of a class of cosine type functional equations. Boletim da Sociedade Paranaense de Matemática, Tome 37 (2017) . doi : 10.5269/bspm.v37i2.29563. http://gdmltest.u-ga.fr/item/29563/