[ napply (Ω \sup S)
| napply mk_equivalence_relation1
[ #A; #B; napply (∀x. iff (x ∈ A) (x ∈ B))
- | nnormalize; #x; #x0; napply mk_iff; #H; nassumption
- | nnormalize; #x; #y; #H; #A; napply mk_iff; #K
+ | nwhd; #x; #x0; napply mk_iff; #H; nassumption
+ | nwhd; #x; #y; #H; #A; napply mk_iff; #K
[ napply (fi ?? (H ?)) | napply (if ?? (H ?)) ]
nassumption
- | nnormalize; #A; #B; #C; #H1; #H2; #H3; napply mk_iff; #H4
+ | nwhd; #A; #B; #C; #H1; #H2; #H3; napply mk_iff; #H4
[ napply (if ?? (H2 ?)); napply (if ?? (H1 ?)); nassumption
| napply (fi ?? (H1 ?)); napply (fi ?? (H2 ?)); nassumption]##]
nqed.
ndefinition intersects ≝ λA.λU,V:Ω \sup A. {x | x ∈ U ∧ x ∈ V }.
#a; #a'; #H; napply mk_iff; *; #H1; #H2
- [ napply (. ((H^-1‡#)‡(H^-1‡#))); nnormalize; napply conj; nassumption
- | napply (. ((H‡#)‡(H‡#))); nnormalize; napply conj; nassumption]
+ [ napply (. ((H^-1‡#)‡(H^-1‡#))); nwhd; napply conj; nassumption
+ | napply (. ((H‡#)‡(H‡#))); nwhd; napply conj; nassumption]
nqed.
(*interpretation "intersects" 'intersects U V = (intersects ? U V).*)