On three-point generalizations of Banach and Edelstein fixed point theorems

Let $X$ be a metric space. Recently in~[1] it was considered a new type of mappings $T\colon X\to X$ which can be characterized as mappings contracting perimeters of triangles. These mappings are defined by the condition based on the mapping of three points of the space instead of two, as it is adopted in many fixed-point theorems. In the present paper we consider so-called $(F,G)$-contracting mappings, which form a more general class of mappings than mappings contracting perimeters of triangles. The fixed-point theorem for these mappings is proved. We prove also a fixed-point theorem for mappings contracting perimeters of triangles in the sense of Edelstein.