The stability of a Cosine-Sine Functional Equation on abelian groups

Ajebbar Omar, Elqorachi Elhoucien, Themistocles M. Rassias

In this paper we establish the stability of the functional equation $$f(x-y)=f(x)g(y)+g(x)f(y)+h(x)h(y)),x,y\in G,$$where $G$ is an abelian group.