This letter extends the K-functional given by Johnen (Lecture Notes in Math., 571 (1977)) so that it may be applied to the study of simultaneous approximation of functions and their partial derivatives.
文摘This letter extends the K-functional given by Johnen (Lecture Notes in Math., 571 (1977)) so that it may be applied to the study of simultaneous approximation of functions and their partial derivatives.
