The equilateral triangle is a symbol of the Holy Trinity. Also, there is the Celtic Trinity Knot opposite. Jacqueline of ahearttoknow.com says, “My daughter and I talked about how God is revealed to us as three different Persons. We labeled one loop as the Father, One as the Son, and One as the Holy Spirit.”
And then there is the circle that excites Andy Math. I thought of myself and my parents on the same circle with the Holy Ghost at the center of the circle, not in a direct way, but that is how He came to me. It sounds wacky and tetched, but it really happened.