Theorem: CompHaus.extensiveRegular_generates_coherent
Proof state before:
case h.h.h.mpr.of.intro.intro.intro.intro.intro.a.intro.intro.intro.intro.mk
X : CompHaus
S : Sieve X
Y : CompHaus
T : Presieve Y
I : Type
hI : Fintype I
Xmap : I → CompHaus
f : (a : I) → Xmap a ⟶ Y
h : T = ofArrows Xmap f
hT : Epi (Sigma.desc f)
he : EffectiveEpiFamily Xmap f ↔ Epi (Sigma.desc f)
φ : (i : I) → Xmap i ⟶ ∐ Xmap := fun i => Sigma.ι Xmap i
F : (∐ fun b => Xmap b) ⟶ Y := Sigma.desc f
Z : Sieve Y := Sieve.generate T
Xs : CompHaus := ∐ fun i => Xmap i
Zf : Sieve Y := Sieve.generate (ofArrows (fun x => Xs) fun x => F)
R : CompHaus
g : R ⟶ Y
W : CompHaus
σ : W ⟶ Y
ψ : R ⟶ ∐ fun i => Xmap i
hW' : ψ ≫ Sigma.desc f = g
⊢ Coverage.saturate
    (ExtensiveRegularCoverage' CompHaus
      (_ : ∀ {X Y Z : CompHaus} (f : Y ⟶ X) (π : Z ⟶ X) [inst : Epi π], Epi Limits.pullback.fst)
      (_ :
        ∀ {α : Type} [inst : Fintype α] {X : CompHaus} {Z : α → CompHaus} (π : (a : α) → Z a ⟶ X) {Y : CompHaus}
          (f : Y ⟶ X) (x : IsIso (Sigma.desc π)), IsIso (Sigma.desc fun x_1 => Limits.pullback.fst)))
    R (Sieve.pullback ψ (Sieve.pullback (Sigma.desc f) Z))
Tactic:
suffices : Sieve.pullback ψ ((Sieve.pullback F) Z) ∈ GrothendieckTopology.sieves
  (ExtensiveRegularCoverage' _ _ _).toGrothendieck R
Proof state after:
case h.h.h.mpr.of.intro.intro.intro.intro.intro.a.intro.intro.intro.intro.mk
X : CompHaus
S : Sieve X
Y : CompHaus
T : Presieve Y
I : Type
hI : Fintype I
Xmap : I → CompHaus
f : (a : I) → Xmap a ⟶ Y
h : T = ofArrows Xmap f
hT : Epi (Sigma.desc f)
he : EffectiveEpiFamily Xmap f ↔ Epi (Sigma.desc f)
φ : (i : I) → Xmap i ⟶ ∐ Xmap := fun i => Sigma.ι Xmap i
F : (∐ fun b => Xmap b) ⟶ Y := Sigma.desc f
Z : Sieve Y := Sieve.generate T
Xs : CompHaus := ∐ fun i => Xmap i
Zf : Sieve Y := Sieve.generate (ofArrows (fun x => Xs) fun x => F)
R : CompHaus
g : R ⟶ Y
W : CompHaus
σ : W ⟶ Y
ψ : R ⟶ ∐ fun i => Xmap i
hW' : ψ ≫ Sigma.desc f = g
this :
  Sieve.pullback ψ (Sieve.pullback F Z) ∈
    GrothendieckTopology.sieves
      (Coverage.toGrothendieck CompHaus (ExtensiveRegularCoverage' CompHaus ?m.588102 ?m.588103)) R
⊢ Coverage.saturate
    (ExtensiveRegularCoverage' CompHaus
      (_ : ∀ {X Y Z : CompHaus} (f : Y ⟶ X) (π : Z ⟶ X) [inst : Epi π], Epi Limits.pullback.fst)
      (_ :
        ∀ {α : Type} [inst : Fintype α] {X : CompHaus} {Z : α → CompHaus} (π : (a : α) → Z a ⟶ X) {Y : CompHaus}
          (f : Y ⟶ X) (x : IsIso (Sigma.desc π)), IsIso (Sigma.desc fun x_1 => Limits.pullback.fst)))
    R (Sieve.pullback ψ (Sieve.pullback (Sigma.desc f) Z))

case this
X : CompHaus
S : Sieve X
Y : CompHaus
T : Presieve Y
I : Type
hI : Fintype I
Xmap : I → CompHaus
f : (a : I) → Xmap a ⟶ Y
h : T = ofArrows Xmap f
hT : Epi (Sigma.desc f)
he : EffectiveEpiFamily Xmap f ↔ Epi (Sigma.desc f)
φ : (i : I) → Xmap i ⟶ ∐ Xmap := fun i => Sigma.ι Xmap i
F : (∐ fun b => Xmap b) ⟶ Y := Sigma.desc f
Z : Sieve Y := Sieve.generate T
Xs : CompHaus := ∐ fun i => Xmap i
Zf : Sieve Y := Sieve.generate (ofArrows (fun x => Xs) fun x => F)
R : CompHaus
g : R ⟶ Y
W : CompHaus
σ : W ⟶ Y
ψ : R ⟶ ∐ fun i => Xmap i
hW' : ψ ≫ Sigma.desc f = g
⊢ Sieve.pullback ψ (Sieve.pullback F Z) ∈
    GrothendieckTopology.sieves
      (Coverage.toGrothendieck CompHaus (ExtensiveRegularCoverage' CompHaus ?m.588102 ?m.588103)) R