Document Type : Original Article

Author

• Abbas Zivari-Kazempour

Department of Mathematics, Ayatollah Borujerdi University, Borujerd, Iran.

Abstract

Let A be a Banach algebra and X be a Banach A-bimodule. In this paper we investigate the stability of the cosine type functional equation
φ(ab,a·y+x·b)=φ(ab,x·b-a·y)=2φ(a,x)φ(b,y),
on module extension Banach algebra U=A+X.

Keywords

• Stability
• Cosine functional equations
• multiplicative function