Heath ID: I.def.15

G.2

A circle is a plane figure contained by one line such that all the straight lines falling upon it from one point among those lying within the figure are equal to one another;

Required for

G.5, G.17, G.19, G.20, G.21, G.23, G.24, G.25, G.26, G.27, G.28, G.8, G.30, G.31, G.32, G.33, G.34, G.35, G.36, G.38, G.39, G.42, G.9, G.43, G.44, G.45, G.46, G.47, G.48, G.49, G.50, G.51, G.52, G.53, G.54, G.55, G.56, G.57, G.58, G.59, G.60, G.61, G.12, G.14, G.15, G.16