Bivariate monotone approximation


Let f be a two variable continuously differentiable real-valued function of certain order on [0, 1] and let L be a linear differential operator involving mixed partial derivatives and suppose that Then there exists a sequence of two-dimensional polynomials This approximation is accomplished quantitatively by the use of a suitable twodimensional first modulus of continuity. © 1991 American Mathematical Society.

Publication Title

Proceedings of the American Mathematical Society