Error estimates of triangular finite elements under a weak angle condition (Q1026458)

By analyzing the interpolation operator of \textit{V. Girault} and \textit{P. A. Raviart} [Finite element methods for Navier-Stokes equations. Theory and algorithms. Springer Series in Computational Mathematics, 5. (Berlin) etc.: Springer- Verlag. (1986; Zbl 0585.65077)] over triangular meshes, the authors prove optimal interpolation error estimates for Lagrange triangular finite elements of arbitrary order under the maximal angle condition in a unified and simple way. The key estimate is only an application of the Bramble-Hilbert lemma