```

sub BM { MODES(TeX => '\\(', Latex2HTML => '\\(', HTML => ''); }; # begin math mode

sub EM { MODES(TeX => '\\)', Latex2HTML => '\\)', HTML => ''); }; # end math mode

sub BDM { MODES(TeX => '\\[', Latex2HTML => '\\[', HTML => '<P ALIGN=CENTER>'); }; #begin displayMath mode

sub EDM { MODES(TeX => '\\]', Latex2HTML => '\\]', HTML => '</P>'); }; #end displayMath mode

```

I searched the OPL and found no problem uses `$BM`, and only one problem uses `$BDM` (`Utah/AP_Calculus_I/set1_Reviews_of_Fundamentals/1210s2p16.pg`). And when I view that one problem, the math that is in "display mode" does not render as math. So either the macro is not being used correctly in this problem, or the macro is not doing what it is supposed to do.

I also find that `EV2` makes use of these macros, replacing `\(`, `\)`, `\[`, and `\]`. However, prior to that, `EV2` makes substitutions using `&math_ev3` and `&display_math_ev3` which I think renders the use of the four macros above pointless.

I'm looking at these in the first place, because I am making a PreTeXt display mode (PTX) and I am trying to give a PTX option for all of these display macros. But I don't really understand what these four do in the first place, so I'm having trouble understanding what the right PTX output should be. If I mimic what happens with that one problem that uses `$BDM`, then it does nothing to wrap math tags around the contents, so I'll do nothing for PTX too. But this seems wrong.

Does anyone know what these macros are supposed to do?