Superconvergence for triangular finite elements

Based on two classes of the orthogonal expansions in a triangle, superconvergence of m-degree triangular finite element solution (for evenm) and its average gradient (for oddm) at symmetric points for a second order elliptic problem are studied. There are no other superconvergence points independent of the coefficients of elliptic equation. Project supported by the National Natural Science Foundation of China (Grant No. 19331021).