The triangle also symbolizes twin rays proceeding from a central point, and when the other ends of these lines are joined, the base line signifies that which is produced by the interaction and interblending of the two formative rays. The apex, the side lines, and the base thus represent the three chief stages of cosmic evolution. The idea is further elaborated in the square pyramid.
The Pythagoreans recognized the triangle as the first regular rectilinear figure, as three is the first odd number -- the one being considered as the origin and unit, out of which all subsequent parts flow. The usual form of the triangle in symbology is equilateral, with the apex up or down. The circle, triangle, and square form another important triad representing stages in evolution. For interlaced triangles,