SUPERSTABILITY OF A GENERALIZED TRIGONOMETRIC FUNCTIONAL EQUATION

Abstract

We will investigate the superstability of the trigonometric functional equation from the following Pexider type functional equation:

f(x+y)−f(x−y) = λ·g(x)h(y), λ is constant,

which is a trigonometric functional equation mixed by the sine and cosine function. More- over, the equation can be considered by the mixed functional equation of the hyperbolic trigonometric functions, several exponential type functions, and Jensen type equation.