proposition: Lemma equivalent_is_eq_reln : forall (a : E) (r : E2P), is_eq_reln a (equivalent a r).
proof: Proof. ir. unfold is_eq_reln in |- *; xd; ir. ap equivalent_refl; au. ap equivalent_symm; au. apply equivalent_trans with y; au. Qed.
imports: set_theory