CONSTRUCTING POINTS THROUGH FOLDING AND INTERSECTION

Abstract

Fix an n ≥ 3. Consider the following two operations: given a line with a specified point on the line we can construct a new line through the point which forms an angle with the new line which is a multiple of π/n (folding); and given two lines we can construct the point where they cross (intersection). Starting with the line y = 0 and the points (0,0) and (1,0) we determine which points in the plane can be constructed using only these two operations for n = 3,4,5,6,8,10,12,24 and also consider the problem of the minimum number of steps it takes to construct such a point.