- 1.
Interaction With Inverse Images. The diagram
i.e. we have
\[ f^{-1}\webleft (U\webright )\mathbin {\triangle }f^{-1}\webleft (V\webright )=f^{-1}\webleft (U\mathbin {\triangle }V\webright ) \]for each $U,V\in \mathcal{P}\webleft (Y\webright )$.
