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Theory and Modern Applications

On the Superstability Related with the Trigonometric Functional Equation


We will investigate the superstability of the (hyperbolic) trigonometric functional equation from the following functional equations: , , , , which can be considered the mixed functional equations of the sine function and cosine function, of the hyperbolic sine function and hyperbolic cosine function, and of the exponential functions, respectively.

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Correspondence to Gwang Hui Kim.

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Open Access This article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Kim, G.H. On the Superstability Related with the Trigonometric Functional Equation. Adv Differ Equ 2009, 503724 (2009).

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