  Mesh adaptation for finite element approximation is a procedure used in
numerous applications. The use of thin and long anisotropic triangles improves
the efficiency of the procedure. When piecewise linear finite elements are
used, the aspect ratio for mesh adaptation is generally dictated by the
absolute value of the (estimated) hessian matrix of the approximated function.
We give in this paper the corresponding aspect ratio for piecewise quadratic
finite elements.
