Theorem: CategoryTheory.Limits.pullback_map_diagonal_isPullback
File: Mathlib/CategoryTheory/Limits/Shapes/Diagonal.lean

tactic: apply IsPullback.of_iso_pullback _ (pullbackDiagonalMapIdIso f g i).symm
state_before: C : Type u_1
inst✝⁵ : Category.{u_2, u_1} C
X Y Z : C
inst✝⁴ : HasPullbacks C
S T : C
f : X ⟶ T
g : Y ⟶ T
i : T ⟶ S
inst✝³ : HasPullback i i
inst✝² : HasPullback f g
inst✝¹ : HasPullback (f ≫ i) (g ≫ i)
inst✝ : HasPullback (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
⊢ IsPullback (fst ≫ f) (map f g (f ≫ i) (g ≫ i) (𝟙 X) (𝟙 Y) i ⋯ ⋯) (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
state_after: case w₁
C : Type u_1
inst✝⁵ : Category.{u_2, u_1} C
X Y Z : C
inst✝⁴ : HasPullbacks C
S T : C
f : X ⟶ T
g : Y ⟶ T
i : T ⟶ S
inst✝³ : HasPullback i i
inst✝² : HasPullback f g
inst✝¹ : HasPullback (f ≫ i) (g ≫ i)
inst✝ : HasPullback (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
⊢ (pullbackDiagonalMapIdIso f g i).symm.hom ≫ fst = fst ≫ f

case w₂
C : Type u_1
inst✝⁵ : Category.{u_2, u_1} C
X Y Z : C
inst✝⁴ : HasPullbacks C
S T : C
f : X ⟶ T
g : Y ⟶ T
i : T ⟶ S
inst✝³ : HasPullback i i
inst✝² : HasPullback f g
inst✝¹ : HasPullback (f ≫ i) (g ≫ i)
inst✝ : HasPullback (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
⊢ (pullbackDiagonalMapIdIso f g i).symm.hom ≫ snd = map f g (f ≫ i) (g ≫ i) (𝟙 X) (𝟙 Y) i ⋯ ⋯

C : Type u_1
inst✝⁵ : Category.{u_2, u_1} C
X Y Z : C
inst✝⁴ : HasPullbacks C
S T : C
f : X ⟶ T
g : Y ⟶ T
i : T ⟶ S
inst✝³ : HasPullback i i
inst✝² : HasPullback f g
inst✝¹ : HasPullback (f ≫ i) (g ≫ i)
inst✝ : HasPullback (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
⊢ CommSq (fst ≫ f) (map f g (f ≫ i) (g ≫ i) (𝟙 X) (𝟙 Y) i ⋯ ⋯) (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)

tactic: simp
state_before: case w₁
C : Type u_1
inst✝⁵ : Category.{u_2, u_1} C
X Y Z : C
inst✝⁴ : HasPullbacks C
S T : C
f : X ⟶ T
g : Y ⟶ T
i : T ⟶ S
inst✝³ : HasPullback i i
inst✝² : HasPullback f g
inst✝¹ : HasPullback (f ≫ i) (g ≫ i)
inst✝ : HasPullback (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
⊢ (pullbackDiagonalMapIdIso f g i).symm.hom ≫ fst = fst ≫ f
state_after: no goals

tactic: ext <;> simp
state_before: case w₂
C : Type u_1
inst✝⁵ : Category.{u_2, u_1} C
X Y Z : C
inst✝⁴ : HasPullbacks C
S T : C
f : X ⟶ T
g : Y ⟶ T
i : T ⟶ S
inst✝³ : HasPullback i i
inst✝² : HasPullback f g
inst✝¹ : HasPullback (f ≫ i) (g ≫ i)
inst✝ : HasPullback (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
⊢ (pullbackDiagonalMapIdIso f g i).symm.hom ≫ snd = map f g (f ≫ i) (g ≫ i) (𝟙 X) (𝟙 Y) i ⋯ ⋯
state_after: no goals

tactic: constructor
state_before: C : Type u_1
inst✝⁵ : Category.{u_2, u_1} C
X Y Z : C
inst✝⁴ : HasPullbacks C
S T : C
f : X ⟶ T
g : Y ⟶ T
i : T ⟶ S
inst✝³ : HasPullback i i
inst✝² : HasPullback f g
inst✝¹ : HasPullback (f ≫ i) (g ≫ i)
inst✝ : HasPullback (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
⊢ CommSq (fst ≫ f) (map f g (f ≫ i) (g ≫ i) (𝟙 X) (𝟙 Y) i ⋯ ⋯) (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
state_after: case w
C : Type u_1
inst✝⁵ : Category.{u_2, u_1} C
X Y Z : C
inst✝⁴ : HasPullbacks C
S T : C
f : X ⟶ T
g : Y ⟶ T
i : T ⟶ S
inst✝³ : HasPullback i i
inst✝² : HasPullback f g
inst✝¹ : HasPullback (f ≫ i) (g ≫ i)
inst✝ : HasPullback (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
⊢ (fst ≫ f) ≫ diagonal i = map f g (f ≫ i) (g ≫ i) (𝟙 X) (𝟙 Y) i ⋯ ⋯ ≫ map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯

tactic: ext <;> simp [condition]
state_before: case w
C : Type u_1
inst✝⁵ : Category.{u_2, u_1} C
X Y Z : C
inst✝⁴ : HasPullbacks C
S T : C
f : X ⟶ T
g : Y ⟶ T
i : T ⟶ S
inst✝³ : HasPullback i i
inst✝² : HasPullback f g
inst✝¹ : HasPullback (f ≫ i) (g ≫ i)
inst✝ : HasPullback (diagonal i) (map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯)
⊢ (fst ≫ f) ≫ diagonal i = map f g (f ≫ i) (g ≫ i) (𝟙 X) (𝟙 Y) i ⋯ ⋯ ≫ map (f ≫ i) (g ≫ i) i i f g (𝟙 S) ⋯ ⋯
state_after: no goals