Revised quadratic subparametric triangular finite element of the second-order accuracy

The modification of quadratic triangular finite element is presented. The considered 7-nodes element allows to obtain diagonal mass-matrix in FEM-scheme with numerical integration. We give a description of corresponding quadrature rule, which has positive coefficients. Error estimates for homogeneous Dirichlet problem for second order PDE are derived. Numerical experiment results, intended to illustrate the strength of the proved theorem, are shown.