Two suggestions.
1. %pi is Maxima's name for the circular constant. You
don't need to assign your own value to pi. Also, Maxima
has built in values for many physical constants.
To access them, load the file 'physconst.'
(%i16) load(physconst)$
(%i17) float(%m_e);
(%o17) 9.109381880000002*10^-31*kg
(%i18) float(%%c);
(%o18) (299792458*m)/s
(%i19) float(%pi);
(%o19) 3.1415926535897931
2. You can change the way Maxima converts a symbol to
TeX by using the 'texput' function. To do this, load
the file 'mactex-utilities'
(%i2) load("mactex-utilities")$
(%i3) texput(st,"\\Sigma_t");
(%o3) \Sigma_t
(%i4) tex(st^2);
$$\Sigma_t^2$$
Barton
-----maxima-admin@math.utexas.edu wrote: -----
>The following is a part of one of my code:
>
> c : 3.0D10$
> e : 4.803242D-10$
> m_e : 9.109534D-28$
> m_p : 1.6726485D-24$
> pi : 3.14159265358979D0$
> \\sigma_T : 6.652448D-25$