So I understand most of the properties of cross products. However I ran into a small complication.
I get that $i\times j = k$, $j\times k = i$. I also understand that $k \times j = -i$ and that $k\times k = j\times j = i\times i = 0$.
But what happens when you have $-k\times k$? Does that also equal $0$, or something else?