CU-P-4P1 Set of 4 tangency points from P to CU
On a general cubic CU we have 4 points of tangency of tangents from some point P to the cubic. They are the intersection points of CU and the P-Polar Conic (CU-P-Co1).

CU-P-4P1 P-points of tangency-01.fig
There is an extra property for the Diagonal Triangle of the Quadrangle QA formed by the touchpoints of the tangents from some point P on CU. The vertices of its Diagonal Triangle also lie on CU and share the same tangential P’ with P, which is QA-Tf2(P).

CU-P-4P1 P-points of tangency-02-plus DT.fig
CU Point Validation
- 2X + P = N has 4 solutions
Properties
- When P = IP (Infinity Point of CU), then CU-P-4P1 = CU-IP-4P1.
- The 4 points CU-P-4P1 form a Quadrangle QA. The Diagonal Triangle QA-DT of QA also has its vertices on CU.
- For each such QA exists an Involutary Conjugate (CU-P-Tf1) mapping any point on CU to another point on CU.
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