##
STABILITY OF QUADRATIC INTERPOLATION POLYNOMIALS IN VERTICES OF TRIANGLES
WITHOUT OBTUSE ANGLES

##
*Josef Dalík*

**Address.** Department of Mathematics, Technical University of Brno,
Zizkova 17, 602 00 Brno, CZECH REPUBLIC
**E-mail:** mddal@fce.vutbr.cz

**Abstract.** 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 $j=2,3,4$.

**AMSclassification.** 65D05

**Keywords.** Quadratic Lagrange interpolation in 2D, stability