On face angles of tetrahedra with a given base

E. V. Nikitenko, Yu. G. Nikonorov

Let us consider the set $\hat{I}\text{c◯}(△ABC)$ of all tetrahedra $ABCD$ with a given non-degenerate base $ABC$ in ${\mathbb{E}}^3$ and $D$ lying outside the plane $ABC$. Let us denote b…