Uniform Superapproximation of the Derivative of Tetrahedral Quadratic Finite Element Approximation

Abstract

In this paper,we will prove the derivative of tetrahedral quadratic finite element approximation is superapproximate to the derivative of the quadratic Lagrange interpolant of the exact solution in the $L^{\infty}$-norm, which can be used to enhance the accuracy of the derivative of tetrahedral quadratic finite element approximation to the derivative of the exact solution.