How to make fonts bigger in **plain tex** math mode?

[Yuri Robbers]

Hi Steve,

I think the file fontch and - for example - \twelvepoint should do the trick for you:

\input fontch

$\forall x \in X, \quad \exists y \leq \epsilon$
$$\forall x \in X, \quad \exists y \leq \epsilon$$

$\twelvepoint\forall x \in X, \quad \exists y \leq \epsilon$
$$\twelvepoint\forall x \in X, \quad \exists y \leq \epsilon$$

\bye

> 
> On 28 Apr 2023, at 09:55, Steve Litt <slitt at troubleshooters.com> wrote:
> 
> Thanks Philip,
> 
> When I ran your code under luatex, here's what happened:
> 
> ===============================================
> [slitt at mydesk plaintex]$ luatex philip.tex 
> This is LuaTeX, Version 1.16.0 (TeX Live 2023) 
> restricted system commands enabled.
> (./philip.tex
> ! Font \sevenrm=cmr7  scaled 1440 not loadable: metric data not found
> or bad. <to be read again> 
> \relax 
> l.12 \font\sevenrm=cmr7  scaled \magstep 2
> 
> ? 
> ===============================================
> 
> So I know it's handling \magstep 2 correctly because it translates to
> 1440, but somehow it has trouble finding the metric data (for cmr7, I
> guess). If I comment out that line, it does the same thing for the
> cmr10 line. It errors out similarly with pdftex, tex, and luatex.
> 
> Thanks,
> 
> SteveT
> 
> 
> Philip Taylor (Hellenic Institute) said on Fri, 28 Apr 2023 09:17:13
> +0100
> 
>>> On 28/04/2023 07:47, Steve Litt wrote:
>>> How do I make fonts bigger in **plain tex** math mode?  
>> 
>> Re-define the fonts and font families used in maths mode —
>> 
>> $\forall x \in X, \quad \exists y \leq \epsilon$
>> $$\forall x \in X, \quad \exists y \leq \epsilon$$
>> 
>> \font\tenrm=cmr10 scaled \magstep 2
>> \font\sevenrm=cmr7  scaled \magstep 2
>> \font\fiverm=cmr5 scaled \magstep 2
>> \font\teni=cmmi10  scaled \magstep 2
>> \font\seveni=cmmi7  scaled \magstep 2
>> \font\fivei=cmmi5 scaled \magstep 2
>> \font\tensy=cmsy10 scaled \magstep 2
>> \font\sevensy=cmsy7 scaled \magstep 2
>> \font\fivesy=cmsy5 scaled \magstep 2
>> \font\tenex=cmex10 scaled \magstep 2
>> \font\tenbf=cmbx10  scaled \magstep 2
>> \font\sevenbf=cmbx7 scaled \magstep 2
>> \font\fivebf=cmbx5 scaled \magstep 2
>> \font\tensl=cmsl10  scaled \magstep 2
>> \font\tentt=cmtt10  scaled \magstep 2
>> \font\tenit=cmti10  scaled \magstep 2
>> 
>> \textfont1=\teni \scriptfont1=\seveni \scriptscriptfont1=\fivei
>> \textfont2=\tensy \scriptfont2=\sevensy \scriptscriptfont2=\fivesy
>> \textfont3=\tenex \scriptfont3=\tenex \scriptscriptfont3=\tenex
>> 
>> $\forall x \in X, \quad \exists y \leq \epsilon$
>> $$\forall x \in X, \quad \exists y \leq \epsilon$$
>> 
>> \end
>> 
>> -- 
>> /Philip Taylor/
>> 
> 
> 
> SteveT
> 
> Steve Litt 
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> http://www.troubleshooters.com/bookstore/thrive.htm
>