In technical writing, I believe expressions like these do not require a definite article:
- Function f(x) is such and such. Graph G has such property. Equation (10) combined with something else gives that.
I mean one should not (or need not?) say "the function f(x)", "the graph G", "the equation (10)", etc..
This is my recollection from what a copy editor did to my writing a long time ago. Is this impression correct? If so, what is the name of this rule? I mean how can I refer others to this point?