1) This list (like most others) does not allow attachments of
any kind. There are a lot of things that can go wrong with
attachments, including viruses, various compatibility issues,
et cetera.
2) Constructive suggestion: For a wide range of equations,
it's not hard to lay them out by hand. For example, in the
example that provoked this thread, the harmonic mean of
a, b, and c is
3
-----------------
1/a + 1/b + 1/c
That's nice and easy to read. Readability helps prevent
typos and other misunderstandings. I can type such a thing
in less time than it takes to tell about it.
The list tolerates mathematical operators, Greek letters,
and other weird symbols reasonably well. In most cases
I just cut-and-paste the symbols I need from somewhere
such as https://www.av8n.com/jsd/play.html
In special cases I typeset the equation in LaTeX, run it
through HeVeA, and cut-and-paste the results.
In simple cases such as e^3 my mail reader (thunderbird)
is clever about superscripts, but in other cases such as
e^-E/kt not so much. Still, you can lay such things out
by hand, by brute force:
-E/kt
e
You can do the same with subscripts. If you want to write
things inline, T_ij is understood to represent subscript {ij}.
Also there are lots of ways to rig up the notation to avoid
subscripts entirely, such as F[ij](x) or F(i,j; x).
3) Another suggestion: For anything too complicated to
lay out in plain email, I typeset it as html, put it on
a web page, and post the link.
With HeVeA, I can typeset seriously complicated equations,
with nice-looking results, without undue effort. This
kills multiple birds with one stone:
++ It solves the typesetting problem.
++ It makes the results available to folks who aren't
subscribed to this list. Some of the web pages that
started out as quick-and-dirty answers to phys-l questions
get thousands of hits every month.
++ It allows me to fix typos. The web page can be
corrected. In contrast, on phys-l you can post errata,
but the original message can never be entirely retracted
or corrected.