The Beckman-Quarles theorem for mappings from to .
The Boundary at Infinity of a Rough CAT(0) Space
We develop the boundary theory of rough CAT(0) spaces, a class of length spaces that contains both Gromov hyperbolic length spaces and CAT(0) spaces. The resulting theory generalizes the common features of the Gromov boundary of a Gromov hyperbolic length space and the ideal boundary of a complete CAT(0) space. It is not assumed that the spaces are geodesic or proper
The Lehmus inequality.
The n -Point Condition and Rough CAT(0)
We show that for n ≥ 5, a length space (X; d) satisfies a rough n-point condition if and only if it is rough CAT(0). As a consequence, we show that the class of rough CAT(0) spaces is closed under reasonably general limit processes such as pointed and unpointed Gromov-Hausdorff limits and ultralimits.
Triangle inequalities from the triangle inequality.
Triangles I: Shapes.
Triangles II: Complex triangle coordinates.
Triangles III: Complex triangle functions.
Trisection de l'angle au moyen du limaçon de Pascal
Two Remarkable Families of Equilateral Triangles within the Pascal Hexagon - A Triumph for Symmetry
Two-distance preserving functions.