FUNCTION: LieTools/SgC2
USAGE: 
SYNOPSIS: SgC2(gpoly) yields the value of the 2nd order Casimir
  operator on a polynomial gpoly in S(g), using its simple
  formula involving the contraction of the differential 
  operators representing the action of basis elements of g
  with the inverse of the Killing form. 
  This procedure requires the declaration and initialization
  of a global BICCgg which is a particular contracion of the 
  inverse Killing form with the structure constants and basis
  elements of g.  One has
          SgC2 = BICCggDD + Euler
  (if you can decipher my mneumonic notation). 
CAVEATS: requires a previously initialized global Lie algebra environment.
  (See LieTools[gSetup].)
EXAMPLE: 
> with(LieTools):
> gSetup(G,2);
Setting up Gtype = G   rnk = 2
> gpoly := g[1]^3;

                                         3
                            gpoly := g[1]

> SgC2(gpoly);

                                      3
                              9/2 g[1]

SEE ALSO: 
