Let p₁ and p₂ be two equivalence relations defined on a non-void set S. Then

Let the relation $$\rho $$ be defined on R as a$$\rho $$b if 1 + ab > 0. Then,

Let f : X $$ \to $$ Y and A, B are non-void subsets of Y, then (where the symbols have their usual interpretation)

Let S, T, U be three non-void sets and f : S $$ \to $$ T, g : T $$ \to $$ U be so that gof : s $$ \to $$ U is surjective. Then,