Stability Results for Some Functional Equations on 2‐Banach Spaces With Restricted Domains

We have a normed abelian group G,.∗,+ and a 2‐pre‐Hilbert space Y with linearly independent elements u and v. Our goal is to prove that any odd map f:G⟶Y satisfying the inequality ‖f(x) + f(y), z‖ ⩽ ‖f(x + y), z‖, z ∈ {u, v}, for all x,y∈G with ‖x‖∗ + ‖y‖∗ ≥ d and some d ≥ 0, is additive. Then, we examined the stability issue correlated with Cauchy and Jensen functional inequalities on restricted domains for maps from normed abelian groups to 2‐Banach spaces. In addition, we determined the asymptotic behaviors of these functional equations.