Module: Mathlib.CategoryTheory.Sites.Continuous

Goal state before:
pp: case refine_1
C : Type u₁
inst✝³ : Category.{v₁, u₁} C
D : Type u₂
inst✝² : Category.{v₂, u₂} D
X : C
E : PreOneHypercover X
F : C ⥤ D
W : C
i₁ i₂ : E.I₀
p₁ : W ⟶ E.X i₁
p₂ : W ⟶ E.X i₂
h : p₁ ≫ E.f i₁ = p₂ ≫ E.f i₂
inst✝¹ : HasPullbacks C
inst✝ : PreservesLimitsOfShape WalkingCospan F
this : HasPullback ((E.map F).f i₁) ((E.map F).f i₂)
T : D
f : T ⟶ F.obj W
k : (E.map F).I₁ i₁ i₂
u : T ⟶ (E.map F).Y k
hf₁ : f ≫ F.map p₁ = u ≫ (E.map F).p₁ k
hf₂ : f ≫ F.map p₂ = u ≫ (E.map F).p₂ k
l : W ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift p₁ p₂ h
hl₁ : l ≫ pullback.fst (E.f i₁) (E.f i₂) = p₁
hl₂ : l ≫ pullback.snd (E.f i₁) (E.f i₂) = p₂
r : E.Y k ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift (E.p₁ k) (E.p₂ k) ⋯
⊢ f ≫ F.map l = u ≫ F.map r

pp: case refine_2
C : Type u₁
inst✝³ : Category.{v₁, u₁} C
D : Type u₂
inst✝² : Category.{v₂, u₂} D
X : C
E : PreOneHypercover X
F : C ⥤ D
W : C
i₁ i₂ : E.I₀
p₁ : W ⟶ E.X i₁
p₂ : W ⟶ E.X i₂
h : p₁ ≫ E.f i₁ = p₂ ≫ E.f i₂
inst✝¹ : HasPullbacks C
inst✝ : PreservesLimitsOfShape WalkingCospan F
this : HasPullback ((E.map F).f i₁) ((E.map F).f i₂)
T : D
f : T ⟶ F.obj W
k : (E.map F).I₁ i₁ i₂
u : T ⟶ (E.map F).Y k
hf₁ : f ≫ F.map p₁ = u ≫ (E.map F).p₁ k
hf₂ : f ≫ F.map p₂ = u ≫ (E.map F).p₂ k
l : W ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift p₁ p₂ h
hl₁ : l ≫ pullback.fst (E.f i₁) (E.f i₂) = p₁
hl₂ : l ≫ pullback.snd (E.f i₁) (E.f i₂) = p₂
r : E.Y k ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift (E.p₁ k) (E.p₂ k) ⋯
⊢ (E.sieve₁ p₁ p₂).arrows (pullback.fst l r)

pp: case refine_3
C : Type u₁
inst✝³ : Category.{v₁, u₁} C
D : Type u₂
inst✝² : Category.{v₂, u₂} D
X : C
E : PreOneHypercover X
F : C ⥤ D
W : C
i₁ i₂ : E.I₀
p₁ : W ⟶ E.X i₁
p₂ : W ⟶ E.X i₂
h : p₁ ≫ E.f i₁ = p₂ ≫ E.f i₂
inst✝¹ : HasPullbacks C
inst✝ : PreservesLimitsOfShape WalkingCospan F
this : HasPullback ((E.map F).f i₁) ((E.map F).f i₂)
T : D
f : T ⟶ F.obj W
k : (E.map F).I₁ i₁ i₂
u : T ⟶ (E.map F).Y k
hf₁ : f ≫ F.map p₁ = u ≫ (E.map F).p₁ k
hf₂ : f ≫ F.map p₂ = u ≫ (E.map F).p₂ k
l : W ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift p₁ p₂ h
hl₁ : l ≫ pullback.fst (E.f i₁) (E.f i₂) = p₁
hl₂ : l ≫ pullback.snd (E.f i₁) (E.f i₂) = p₂
r : E.Y k ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift (E.p₁ k) (E.p₂ k) ⋯
⊢ f = ⋯.lift f u ?refine_1 ≫ F.map (pullback.fst l r)

Tactic:
· apply (IsPullback.map _ (.of_hasPullback _ _)).hom_ext <;>
      simp [l, r, ← Functor.map_comp, hf₁, hf₂]

Goal state after:
case refine_2
C : Type u₁
inst✝³ : Category.{v₁, u₁} C
D : Type u₂
inst✝² : Category.{v₂, u₂} D
X : C
E : PreOneHypercover X
F : C ⥤ D
W : C
i₁ i₂ : E.I₀
p₁ : W ⟶ E.X i₁
p₂ : W ⟶ E.X i₂
h : p₁ ≫ E.f i₁ = p₂ ≫ E.f i₂
inst✝¹ : HasPullbacks C
inst✝ : PreservesLimitsOfShape WalkingCospan F
this : HasPullback ((E.map F).f i₁) ((E.map F).f i₂)
T : D
f : T ⟶ F.obj W
k : (E.map F).I₁ i₁ i₂
u : T ⟶ (E.map F).Y k
hf₁ : f ≫ F.map p₁ = u ≫ (E.map F).p₁ k
hf₂ : f ≫ F.map p₂ = u ≫ (E.map F).p₂ k
l : W ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift p₁ p₂ h
hl₁ : l ≫ pullback.fst (E.f i₁) (E.f i₂) = p₁
hl₂ : l ≫ pullback.snd (E.f i₁) (E.f i₂) = p₂
r : E.Y k ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift (E.p₁ k) (E.p₂ k) ⋯
⊢ (E.sieve₁ p₁ p₂).arrows (pullback.fst l r)

case refine_3
C : Type u₁
inst✝³ : Category.{v₁, u₁} C
D : Type u₂
inst✝² : Category.{v₂, u₂} D
X : C
E : PreOneHypercover X
F : C ⥤ D
W : C
i₁ i₂ : E.I₀
p₁ : W ⟶ E.X i₁
p₂ : W ⟶ E.X i₂
h : p₁ ≫ E.f i₁ = p₂ ≫ E.f i₂
inst✝¹ : HasPullbacks C
inst✝ : PreservesLimitsOfShape WalkingCospan F
this : HasPullback ((E.map F).f i₁) ((E.map F).f i₂)
T : D
f : T ⟶ F.obj W
k : (E.map F).I₁ i₁ i₂
u : T ⟶ (E.map F).Y k
hf₁ : f ≫ F.map p₁ = u ≫ (E.map F).p₁ k
hf₂ : f ≫ F.map p₂ = u ≫ (E.map F).p₂ k
l : W ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift p₁ p₂ h
hl₁ : l ≫ pullback.fst (E.f i₁) (E.f i₂) = p₁
hl₂ : l ≫ pullback.snd (E.f i₁) (E.f i₂) = p₂
r : E.Y k ⟶ pullback (E.f i₁) (E.f i₂) := pullback.lift (E.p₁ k) (E.p₂ k) ⋯
⊢ f = ⋯.lift f u ⋯ ≫ F.map (pullback.fst l r)