QA-P16: QA-Harmonic Center

The triangle formed by the 3 QA-versions of QG-P12 (Inscribed Harmonic Conic Center) is perspective with the QA-Diagonal Triangle. Their Perspector is QA-P16.
QA-P16 partakes in many QA-Parallelities and with many QA-Crosspoints (see QA-3 and QA-5).
QA-P16 is named harmonic because its construction is based on projective principles leading to harmonic properties.
QA-P16 in a Quadrangle is the counterpart of QL-P13 in a Quadrilateral.

Construction:
Construct QA-P16 as the Complement of the Isotomic Conjugate of the AntiComplement of QA-P1 wrt the QA-Diagonal Triangle
= QA-P10-Ceva conjugate of QA-P1 wrt the QA-Diagonal Triangle . QA-P16 is the perspector of the triangles formed by the 3 QA-versions of QG-P12 (Inscribed Harmonic Conic Center) and the QA-Diagonal Triangle. QA-P16 is the intersection point of the tangents at the vertices of the QA-Diagonal Triangle and QA-P10 to the QA-DT-P10 Cubic (QA-Cu3).

Coordinates:

1st CT-coordinate:
p (2 p + q + r)
1st DT-coordinate:
p2

Properties:
• QA-P16 lies on these QA-lines:
QA-P1.QA-P21          (-1 : 2 => QA-P16 = Reflection QA-P21 in QA-P1)
QA-P10.QA-P19        (-1 : 3)
• QA-P16 lies on this QG-line:

• QA-P16 is the Reflection of QA-P19 in QA-P31.
• QA-P16 is the QA-Involutary Conjugate (see QA-Tf2) of QA-P10.
• QA-P16 = QA-P10-Ceva conjugate of QA-P1 wrt the QA-Diagonal Triangle.
• QA-P16 is collinear with QG-P1, QG-P12, QG-P13, QL-P13 on QG-L2.
• QA-P16 is the 4th Perspective Point in the row QG-P13, QG-P12, QG-P1 on line QG-L2 (see Ref-26 Perspective Fields part II).
• QA-P16 lies on the Conic QA-Co5.
• QA-P16 lies on the Conic through P1, P2, P3, P4 and QA-P1.
• QA-P16 lies on the Cubics QA-Cu3 and QA-Cu4.
• QA-P16 is the pole of the Cubics QA-Cu1QA-Cu5 when seen as IsoCubics wrt the QA-Diagonal Triangle and with the Involutary Conjugate as Isoconjugation.
• QA-P16 is the intersection point of the tangents at the vertices of the QA-Diagonal Triangle and QA-P10 to the QA-DT-P10 Cubic (QA-Cu3).
• QA-P16 is the Complement of QA-P19 wrt the QA-Diagonal Triangle.
• QA-P16 is the AntiComplement of QA-P31 wrt the QA-Diagonal Triangle.
• The 3 versions of QG-L2 in a Quadrangle concur in QA-P16.
• QA-P16 is the perspector the QA-Diagonal Triangle and the tangential triangle of the QA-Nine-point conic wrt the QA-Diagonal Triangle (note Randy Hutson).
• QA-P16 is the Radical Center of the 3 QA-versions of QL-Ci1: Circumcircle QL-DT (Eckart Schmidt, July, 2012).
• Let P1P2P3P4 be a Quadrangle. Let Qi (i=1,2,3,4) be the center of the circum-conic to Diagonal Triangle with perspector Pi. QA-P16 is the common intersection point of lines Pi.Qi (Angel Montesdeoca, January 18, 2015).
• QA-P16 is the Perspector of the mutual Triple Triangles (see QA-Tr-1) of QG-P1, QG-P12, QG-P13, QL-P13.