Definitions A polygon is a closed path of straight line segments in R 2 . These segments are also called edges of the polygon, and the intersection of two adjacent edges is a vertex of the polygon. Thus every polygon with n vertices has n edges. Every simple polygon divides R 2 into an interior and an exterior region. A simple polygon is convex if the internal angle formed at each vertex is smaller than 180 o .
P is P itself.
The 3-coins algorithm was developed independently by Graham and Sklansky in 1972, to find convex hulls. Graham proposed using the 3-coins algorithm to find the convex hull of a set of n points in R 2 . Sort the remaining n-1 points radially, using p 0 as the origin. Connect the remaining points in order. This forms the convex hull of the original set of n points.