If the incircle is tangent to the sides "AB", "BC", "CD", "DA" at "T1", "T2", "T3", "T4" respectively, and if "N1", "N2", "N3", "N4" are the isotomic conjugates of these points with respect to the corresponding sides (that is, "AT1" = "BN1" and so on), then the "Nagel point" of the tangential quadrilateral is defined as the intersection of the lines "N1N3" and "N2N4". Both of these lines divide the perimeter of the quadrilateral into two equal parts. More importantly, the Nagel point "N", the "area centroid" "G", and the incenter "I" are collinear in this order, and "NG" = 2"GI". This line is called the "Nagel line" of a tangential quadrilateral.