Abstract Let S , H X be groups. For two given biadditive functions A : 2 → B and for unknown mappings T g we will study the functional equation ( x ), y )) = x, )), ∈ S, which is a generalization of orthogonality in Hilbert spaces.

Abstract Let X , Y be linear spaces over a field $${\mathbb {K}}$$ K . Assume that $$f :X^2\rightarrow Y$$ f : X 2 → Y satisfies the general equation with respect...