| (1) | \begin{equation} \forall \, x, y, z \in X : f(f(x, y), z) = f(x, f(y, z)) \end{equation} |
| (2) | \begin{equation} \exists \, I \in X : \forall \, x \in X : f(I, x) = f(x, I) = x \end{equation} |
| (1) | \begin{equation} \forall \, x, y, z \in X : f(f(x, y), z) = f(x, f(y, z)) \end{equation} |
| (2) | \begin{equation} \exists \, I \in X : \forall \, x \in X : f(I, x) = f(x, I) = x \end{equation} |