Alexander polynomial of a knot
= Alexander polynomial of a knot
{c}
{title2=$\Delta_K(t)$}
{wiki=Alexander_polynomial}
Up to multiplication by a unit $\pm t^n$, the Alexander polynomial is
$$
\Delta_K(t)=\det(tA-A^T).
$$
It satisfies $\Delta_K(t^{-1})\doteq\Delta_K(t)$ and $\Delta_K(1)=\pm1$.