On the Superstability of the Pexider Type Trigonometric Functional Equation.

We will investigate the superstability of the (hyperbolic) trigonometric functional equation from the following functional equations: f(x + y) ± g(x - y) = λf(x)g(y) and f(x + y) ± g(x - y) = 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. [ABSTRACT FROM AUTHOR]