If you are using the new 2011 Formats Guidelines, Rule 5 is no longer in effect because 1997 Formats is no longer in effect. Don't even go there! I looked in the 2011 Guidelines index and found a list of all the math (and other) symbols in Appendix G and the guidelines for using them in Section 1. As before, we follow print. We braille the symbol and not the word when the symbol only is used in print. The symbol is listed on the Special Symbols page or at the location where it occurs. It will take a little time to get used to the new guidelines. Do not fear the Index.