Maximizing maximal angles for plane straight-line graphs

Let G¿=¿(S, E) be a plane straight-line graph on a finite point set in general position. The incident angles of a point p¿¿¿S in G are the angles between any two edges of G that appear consecutively in the circular order of the edges incident to p. A plane straight-line graph is called ¿-open if each vertex has an incident angle of size at least ¿. In this paper we study the following type of question: What is the maximum angle ¿ such that for any finite set of points in general position we can find a graph from a certain class of graphs on S that is ¿-open? In particular, we consider the classes of triangulations, spanning trees, and paths on S and give tight bounds in most cases