2. Region(face) colourings Definitions 46: A edge of the graph is called a bridg if the edge is not in any circuit. a connected planar graph is called a map, If the graph has not any bridge Definition 47: A proper region coloring of a map g is an assignment of colors to the region of G, one color to each region, such that adiacent regions receive different colors. An proper region coloring in which k colors are used is a k-region coloring. A map g is k-region colorable if there exists an s coloring of g for some s sk. The minimum integer k for which G is k- region colorable is called the region chromatic number. We denoted by x (G). If x (G) k, then g is k-region chromatic.▪ 2. Region(face) colourings ▪ Definitions 46: A edge of the graph is called a bridge, if the edge is not in any circuit. A connected planar graph is called a map, If the graph has not any bridge. ▪ Definition 47: A proper region coloring of a map G is an assignment of colors to the region of G, one color to each region, such that adjacent regions receive different colors. An proper region coloring in which k colors are used is a k-region coloring. A map G is k-region colorable if there exists an s￾coloring of G for some s  k. The minimum integer k for which G is k- region colorable is called the region chromatic number. We denoted by *(G). If *(G) = k, then G is k-region chromatic