An explicit description of the basic Lagrange polynomials in two variables related to a six-tuple $a^1,\dots ,a^6$ of nodes is presented. Stability of the related Lagrange interpolation is proved under the following assumption: $a^1,\dots ,a^6$ are the vertices of triangles $T_1,\dots ,T_4$ without obtuse inner angles such that $T_1$ has one side common with $T_j$ for $j=2,3,4$.
@article{107703,
author = {Josef Dal\'\i k},
title = {Stability of quadratic interpolation polynomials in vertices of triangles without obtuse angles},
journal = {Archivum Mathematicum},
volume = {035},
year = {1999},
pages = {285-297},
zbl = {1051.41002},
mrnumber = {1744516},
language = {en},
url = {http://dml.mathdoc.fr/item/107703}
}
Dalík, Josef. Stability of quadratic interpolation polynomials in vertices of triangles without obtuse angles. Archivum Mathematicum, Tome 035 (1999) pp. 285-297. http://gdmltest.u-ga.fr/item/107703/
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