A stability result for a generalized trigonometric-quadratic functional equation with one unbounded function
نویسنده
چکیده
A generalized trigonometric-quadratic functional equation of the form F(x+ y) + G(x− y) = 2H(x)K(y) + L(x) +M(y) over the domain of an abelian group and the range of the complex field is considered. Its stability is established based on the assumption that the function K is unbounded. Subject to certain natural conditions, explicit shapes of the functions H and K are determined. Several existing related results are derived as direct consequences. Key–Words: Quadratic functional equation, trigonometric functional equation, stability, unboundedness, abelian group, additive function.
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