Drop a perpendicular from point C (3.2.43)
Create twelve equal divisions between A and B
Erect a perpendicular at A and B
Mark the height of point C on perpendicular A and B, then make six equal divisions on each perpendicular
Establish C' with the height of C' reflected below the baseline
Extend lines from C through the lower five markers on perpendicular A and B
Extend lines from C' through each marker along the baseline. Extend until the line intersects the corresponding line from C
Complete the arc using a batten, drawing a curve through each of the intersections