We distinguish the rational points P[sub]i [/sub]= (i/n,1) and the irrational points Q = (i/(n+[br][math]\pi[/math]/n,0). The lines f and g show they are distinct points of the graph of the Dirichlet function:[br][math]\delta[/math](x)=1 for rational, and [math]\delta[/math](x)= 0 for irrational x.
[sub]i[/sub]You may change the values of n, and i (recommended to have the same upper bound).[br]