Notes on diameters, centers, and approximating trees of δ-hyperbolic geodesic spaces and graphs

We present simple methods for approximating the diameters, radii, and centers of finite sets in δ-hyperbolic geodesic spaces and graphs. We also provide a simple construction of distance approximating trees of δ-hyperbolic graphs G on n vertices with an additive error O(δlog2n) comparable with that given by M. Gromov.