-- Mathlib/CategoryTheory/Quotient.lean
lemma lift_unique' (F₁ F₂ : Quotient r ⥤ D) (h : functor r ⋙ F₁ = functor r ⋙ F₂) :
    F₁ = F₂

Proof state:
case hΦ
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ functor r ⋙ F₁ = functor r ⋙ F₂

Tactic:
rw [h]

Result:
no goals

Proof state:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h✝ : functor r ⋙ F₁ = functor r ⋙ F₂
X Y : C
f g : X ⟶ Y
h : r f g
⊢ F₂.map ((functor r).map f) = F₂.map ((functor r).map g)

Tactic:
rw [Quotient.sound r h]

Result:
no goals

Proof state:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ F₁ = F₂

Tactic:
rw [lift_unique r (functor r ⋙ F₂) _ F₂ rfl]

Result:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ F₁ = lift r (functor r ⋙ F₂) ?m.20389

C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ ∀ (x y : C) (f₁ f₂ : x ⟶ y), r f₁ f₂ → (functor r ⋙ F₂).map f₁ = (functor r ⋙ F₂).map f₂

Proof state:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ F₁ = lift r (functor r ⋙ F₂) ?m.20389

C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ ∀ (x y : C) (f₁ f₂ : x ⟶ y), r f₁ f₂ → (functor r ⋙ F₂).map f₁ = (functor r ⋙ F₂).map f₂

Tactic:
swap

Result:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ ∀ (x y : C) (f₁ f₂ : x ⟶ y), r f₁ f₂ → (functor r ⋙ F₂).map f₁ = (functor r ⋙ F₂).map f₂

C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ F₁ = lift r (functor r ⋙ F₂) ?m.20389

Proof state:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ ∀ (x y : C) (f₁ f₂ : x ⟶ y), r f₁ f₂ → (functor r ⋙ F₂).map f₁ = (functor r ⋙ F₂).map f₂

Tactic:
rintro X Y f g h

Result:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h✝ : functor r ⋙ F₁ = functor r ⋙ F₂
X Y : C
f g : X ⟶ Y
h : r f g
⊢ (functor r ⋙ F₂).map f = (functor r ⋙ F₂).map g

Proof state:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h✝ : functor r ⋙ F₁ = functor r ⋙ F₂
X Y : C
f g : X ⟶ Y
h : r f g
⊢ (functor r ⋙ F₂).map f = (functor r ⋙ F₂).map g

Tactic:
dsimp

Result:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h✝ : functor r ⋙ F₁ = functor r ⋙ F₂
X Y : C
f g : X ⟶ Y
h : r f g
⊢ F₂.map ((functor r).map f) = F₂.map ((functor r).map g)

Proof state:
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ F₁ = lift r (functor r ⋙ F₂) ⋯

Tactic:
apply lift_unique

Result:
case hΦ
C : Type u_3
inst✝¹ : Category.{u_1, u_3} C
r : HomRel C
D : Type u_4
inst✝ : Category.{u_2, u_4} D
F₁ F₂ : Quotient r ⥤ D
h : functor r ⋙ F₁ = functor r ⋙ F₂
⊢ functor r ⋙ F₁ = functor r ⋙ F₂