Journal of Inequalities and Applications
Volume 2010 (2010), Article ID 897123, 14 pages
Research Article

On the Superstability of the Pexider Type Trigonometric Functional Equation

Department of Mathematics, Kangnam University, Yongin, Gyeonggi 446-702, South Korea

Received 23 October 2009; Accepted 3 January 2010

Academic Editor: Yeol Je Cho

Copyright © 2010 Gwang Hui Kim. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We will investigate the superstability of the (hyperbolic) trigonometric functional equation from the following functional equations: f(x+y)±g(xy)=λf(x)g(y) andf(x+y)±g(xy)=λg(x)f(y), which can be considered the mixed functional equations of the sine function and cosine function, the hyperbolic sine function and hyperbolic cosine function, and the exponential functions, respectively.