The 7P-Circular Cubic 7P-s-Cu1 is invariant under the CB-conjugation 7P-s-Tf1 with a pivot.
This means that:
• the CB-conjugate of any point on the cubic is again a point on this cubic, and
• all lines connecting a point P on 7P-s-Cu1 and its conjugate 7P-s-Tf1(P) will pass through a common point. This common point is called the CB-pivot 7P-s-P2 and also lies on the cubic.
This special property was first mentioned by Eckart Schmidt. See Ref-66, QPG-message #652.
