| The segments that make the angle must belong to the same face and not be collinear. |
| As given earlier, the three relevant intersection points for six points on the circle will be collinear. |
| If all points are collinear, it has zero area and is represented by a segment. |
| If four of the points are collinear, or two of the points coincide, no conic is created. |
| The use of collinear beam geometry facilitates the alignment of the overlap of the two foci and ensures high image quality. |
| It then follows from the Menelaus theorem, that every three such points are collinear provided all or two of the bisectors are external. |
