# [texhax] Q: bold variables in math mode

Uwe Lueck uwe.lueck at web.de
Wed Jun 1 12:22:53 CEST 2011

"D. R. Evans" <doc.evans at gmail.com> wrote 31.05.2011 21:21:34:
> I need to be able to typeset something like:
>   A = CM
> in math mode where A and M are bold, but C is roman.
>
> As long as I don't redefine \bf, then the following works:
>   ${\bf A} = {\rm C} {\bf M}$
>
> But I have:
>   \font\bf=ec-lmbx12 at 10.5pt
> and now when I type the math mode expression, A, C and M are all rendered
> in math italic instead of bold.
>
> How do I get A and M to render in the bold face I am defining with the
> above \font\bf command?

*Guessing* from TeXbook pp. 350f.:

\font\tenbf=ec-lmbx12 at 10.5pt

may suffice if you keep

\newfam\bffam \def\bf{\fam\bffam\tenbf} \textfont\bffam=\tenbf