The Cross and Triangle is a symbol used by the Golden Dawn to represent the order. The symbol is described as The Cross and Triangle, the Supernal Sphiroth, and the "Red Cross of Tiphareth".
The symbol represent illumination through life, represented by the symbolism of the Crucifixion wherein the self-sacrifice of one brings equilibration and harmony to all.
Some or all of this article used the following publication as a resource:
The Essential Golden Dawn: An Introduction to High Magic. Chic Cicero & Sandra Tabatha Cicero. 2003. Llewellyn Worldwide. St. Paul, MN.