9-point conic (generalisation du cercle des 9 points)
Given four points A, B, C, D (in red), determine:
- the midpoints of AB, AC, .... (six points, blue circles)
- the three intersections (blue crosses) of AB & CD, AC & BD, AD & BC
There is a conic (blue conic) through these 9 points.
Furthermore, given an arbitrary fifth point E (orange), the conic (green) through these five points A, B, C, D, E has its center on the blue conic