# [OS X TeX] bold italic vector expressions in Plain TeX

Ross Moore ross.moore at mq.edu.au
Tue Jun 30 22:05:10 CEST 2020

Hello Dan,

On 01/07/2020, at 4:56, "Daniel Drucker" <aa1856 at wayne.edu<mailto:aa1856 at wayne.edu>> wrote:

Dear All,

I am using TeXShop 4.44 on a mid-2011 iMac running Mac OS 10.13.6 (High Sierra).
That’s the latest version of the Mac OS that’s compatible with my iMac. I also
have a fairly new MacBook Pro, but I like using TeX on the iMac because it has
a 27” screen.

I run into problems when I try to use bold extended text italic in Plain TeX’s
math mode. I’d appreciate any suggestions you might have in how to use bold
extended text italic painlessly in math mode.

Font handling in math mode is quite different to in text mode, due to differences in spacing, and the need to handle superscripts and subscripts properly.

You need the concept of a math-family of fonts.
See The TeXBook  for details, ...

... or stick to LaTeX and packages,
where this has already been fully worked out.

I’m attaching a short document that illustrates the behavior I’m seeing and the
problems I’m having.

Thanks,
Dan Drucker

Hope this helps.
Stay safe.

Ross

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\magnification\magstep2
\nopagenumbers
\font\bx=cmbxti10
\def\ts{\thinspace}
\def\bi{{\bx i}} \def\bj{{\bx j}} \def\bk{{\bx k}}
\def\bv{{\bx v}} \def\bw{{\bx w}}
\def\bvv{\hbox{\bx v}} \def\bww{\hbox{\bx w}}
\def\bvvv{\hbox{\bx v\ts}} \def\bwww{\hbox{\bx w\ts}}

{\bx This looks fine, but it's plain text, not math.}

$3\bi + 5\bj$. Math mode has overridden bold italic here. Why?

{\bx 3\bi\ $+$ 4\bj}. The numbers are also in bold italic.

3\bi\ + 4\bj\ + 5\bk. This looks fine, but it's not in math mode.

4\bv\ - 5\bw. The minus sign needs to be in math mode.

4\bv\ $-$ 5\bw. Now the minus sign looks right.

$4v-5w$. Here's the spacing in ordinary math mode without bold italic.

$c$\bv\ $-d$\bw. Math mode doesn't fix the spacing after the minus sign.

$c$\bv\ $-$ $d$\bw. This looks better, but the coding is awkward.

$c\bvv+d\bww$. hboxes help, but the spacing isn't quite right.

$c\bvvv+d\bwww$. Adding thinspaces still doesn't yield correct spacing.

$c\bvv-d\bww$. Here's the same experiment, but with a minus sign.

$c\bvvv-d\bwww$. Spacing is still a problem.

\bye

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