Mystic Hexagram Theorem (1655)

Theorem: Suppose you have any ellipse. Choose any six distinct points on the ellipse, and form a hexagon by connecting the six points, in order, with straight-line segments. As discussed in Menelaus' Theorem above, each of these line segments has an extension that passes through a consecutive pair of points, but extends to infinity. Pascal's Mystic Hexagram Theorem guarantees that the points of intersection of the extensions of the opposite sides of the hexagram must lie on the same line. (If you are confused about the term "opposite sides', consider numbering the sides, in order, from 1 through 6; then side 1 is opposite side 4, side 2 is opposite side 5, and side 3 is opposite side 6.)

Author: Blaise Pascal presented this theorem, with a proof, when he was just 16 years old, in approximately 1638.

Importance: Similar to that for Desargues Theorem.