Some $\mframed{math}$ questions

[Mojca Miklavec <mojca.miklavec.lists@gmail.com>]

Hello,

I would like to ask a couple of questions about frames and numbers in
math formulas.

1. What's the best way to frame a formula like here:

\placeformula
\startformula
\mframed{x^2+y^2=z^2}
\stopformula

The problem is that:
- formula number is shifted downwards in comparison to the formula
without a number
- I don't know how to do the settings (frame color, frame offset)
globally. There's no \setupmframed[...] command. It's probably
possible to use a sort of
\setupframed[whatever_setting_influencing_only_mframed],
but I don't know how.

2. What's the general strategy when doing evel stuff with formula
numbering? I would like to use \eqalign and then number formulas like
on the following example:

z^2=x^2+y^2    (1)
   =(x'-x_0)^2+(y'-y_0)^2 % no number
   =R^2\cos^2(\phi)    (2)

Can I somehow number the formulas (1), (2), (3.a), (3.b), (3.c), (4),
(5.1), (5.2)? I would like to manually provide where to start and stop
numbering with x.a or x.1, x.2.

3. How can I put more than one equation in a row and number all of
them (as if they were placed in three columns)?

4. How can I move the formula number one row lower in case that the
formula is too long and if it would overlap with the formula number
otherwise?

Thank you very much for any help,
    Mojca