\begin{tikzpicture}[baseline]
\node (x) at (0,0){};
    \draw[->] (x.45)-- (.5,.5);
    \draw[->] (x.135) -- (-.5,.5);
    \draw (x.315) -- (.5,-.5);
    \draw (x.45) -- (-.5,-.5);
\end{tikzpicture}
=a^{-1}
\begin{tikzpicture}[baseline]
    \draw[<-] (1.5,.5) .. controls (2,0) .. (1.5,-.5);
    \draw[<-] (2.5,.5) .. controls (2,0) .. (2.5,-.5);
\end{tikzpicture}
-a^{-2}
\begin{tikzpicture}[baseline]
    \draw (3.5,.5) .. controls (4,0) .. (4.5,.5);
    \draw (3.5,-.5) .. controls (4,0) .. (4.5,-.5);
\end{tikzpicture}
