On the superstability of the cosine and sine type functional equations

Fouad Lehlou, Mohammed Moussa, Ahmed Roukbi, Samir Kabbaj

Abstract


In this paper, We study the superstablity problem of the cosine and sine type functional equations:

f(xσ(y)a)+f(xya)=2f(x)f(y)

and

f(xσ(y)a)-f(xya)=2f(x)f(y),

where f:S → C is a complex valued function; S is a semigroup; σ is an involution of S and a is a fixed element in the center of S.


Keywords


functional equation; superstablity; stablity

Mathematics Subject Classification (2010)


Primary 39B32; Secondary 39B72.

References


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