Kernelled Quasidifferential for a Quasidifferentiable Function in Two-Dimensional Space

For a quasidifferentiable function f defined on R 2 , it is proved, in the sense of Demyanov and Rubinov, that the following assertion [∂f (x),∂f (x)]∈Df (x) (∂f (x) + ∂f (x)), [∂f (x),∂f (x)]∈Df (x) (∂f (x) − ∂f (x)) ∈ Df (x) in this paper, where Df (x) denotes the set of all quasidifferentials of f at x. It is shown that this way can be viewed as an approach to determining or choosing a representative of the equivalent class of quasidifferentials of f at x, in the two-dimensional case.