[table][tr][td]1[/td][td]Construct two circles that run through each other centers.[/td][/tr][tr][td]2[/td][td]Define the intersection points N and O of both circles.[/td][/tr][tr][td]3[/td][td]Connect the midpoints D and E with the intersection points N and O and define the points 1, 2, 3 and 4.[/td][/tr][tr][td]4[/td][td]Construct the circular arcs from 3 to 4 with center D and from 1 to 2 with midpoint E.[/td][/tr][/table]