QL-P23: Center of the Inscribed Midline Hyperbola
QL-P23 is the center of the Inscribed Midline Hyperbola. This is the conic touching the defining lines of the Reference Quadrilateral and with the Newton Line as asymptote. See Paragraph QL-Co2.
l (m - n) ((l m + l n + m n)2 - 4 m n (l2 + m n))
m2 n2 (m2-n2)