QL-P19: Midpoint of QL-P1 and QL-P7

QL-P19 is the Midpoint of QL-P1 and QL-P7.
Special about this point is that it lies on QL-L3, the QL-Pedal Line.
Besides that it has a distance relation with the M3D Line (QL-L9).
 QL-P19-Midpoint QL-P1 and QL-P7                      
1st CT-coordinate:
            (a2 m n - SB l m - SC l n) (3 m n - l m - l n)
1st DT-coordinate:
            Sa (m2-n2)2 - Sb (l2-n2) n2 - Sc (l2-m2) m2


        QL-P1.QL-P7 = QL-L5    (1 : 1 => QL-P19 = Midpoint QL-P1, QL-P7)