WATCHING SYSTEMS OF TRIANGULAR GRAPHS

A watching system in a graph G = (V;E) is a set W = f!1; !2; : : : ; !kg, where !i = (vi;Zi); vi 2 V and Zi is a subset of closed neighborhood of vi such that the sets LW(v) = f!i : v 2 Zig are non-empty and distinct, for any v 2 V . In this paper, we study the watching systems of line graph Kn which is called triangular graph and denoted by T(n). The minimum size of a watching system of G is denoted by !(G). We show that !(T(n)) = d2n 3 e.