'Returns the trailing coefficient of ``f``.
Examples
>>> from sympy import Poly
>>> from sympy.abc import x
>>> Poly(x**3 + 2*x**2 + 3*x, x).TC()
0'

def TC(f):

    if hasattr(f.rep, 'TC'):
        result = f.rep.TC()
    else:
        raise OperationNotSupported(f, 'TC')
    return f.rep.dom.to_sympy(result)
