-- Mathlib/GroupTheory/Perm/Cycle/Concrete.lean
theorem IsCycle.existsUnique_cycle {f : Perm α} (hf : IsCycle f) :
    ∃! s : Cycle α, ∃ h : s.Nodup, s.formPerm h = f

Proof state:
case intro.intro.intro.refine_1
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
f : Perm α
hf : f.IsCycle
val✝ : Fintype α
x : α
hx : f x ≠ x
hy : ∀ ⦃y : α⦄, f y ≠ y → f.SameCycle x y
⊢ (↑(f.toList x)).formPerm ⋯ = f

Tactic:
simp [formPerm_toList, hf.cycleOf_eq hx]

Result:
no goals

Proof state:
case intro.intro.intro.refine_2
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
f : Perm α
hf : f.IsCycle
val✝ : Fintype α
x : α
hx : f x ≠ x
hy : ∀ ⦃y : α⦄, f y ≠ y → f.SameCycle x y
⊢ ∀ (y : Cycle α), (fun s => ∃ (h : s.Nodup), s.formPerm h = f) y → y = ↑(f.toList x)

Tactic:
rintro ⟨l⟩ ⟨hn, rfl⟩

Result:
case intro.intro.intro.refine_2.mk.intro
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hx : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) x ≠ x
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
⊢ Quot.mk (⇑(IsRotated.setoid α)) l = ↑((Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).toList x)

Proof state:
case intro.intro.intro.refine_2.mk.intro.refine_1
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
hx : l.length < 2
⊢ l.formPerm = 1

Tactic:
rw [formPerm_eq_one_iff _ hn]

Result:
case intro.intro.intro.refine_2.mk.intro.refine_1
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
hx : l.length < 2
⊢ l.length ≤ 1

Proof state:
case intro.intro.intro
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
f : Perm α
hf : f.IsCycle
val✝ : Fintype α
x : α
hx : f x ≠ x
hy : ∀ ⦃y : α⦄, f y ≠ y → f.SameCycle x y
⊢ ∃! s, ∃ (h : s.Nodup), s.formPerm h = f

Tactic:
refine ⟨f.toList x, ⟨nodup_toList f x, ?_⟩, ?_⟩

Result:
case intro.intro.intro.refine_1
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
f : Perm α
hf : f.IsCycle
val✝ : Fintype α
x : α
hx : f x ≠ x
hy : ∀ ⦃y : α⦄, f y ≠ y → f.SameCycle x y
⊢ (↑(f.toList x)).formPerm ⋯ = f

case intro.intro.intro.refine_2
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
f : Perm α
hf : f.IsCycle
val✝ : Fintype α
x : α
hx : f x ≠ x
hy : ∀ ⦃y : α⦄, f y ≠ y → f.SameCycle x y
⊢ ∀ (y : Cycle α), (fun s => ∃ (h : s.Nodup), s.formPerm h = f) y → y = ↑(f.toList x)

Proof state:
case intro.intro.intro.refine_2.mk.intro
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hx : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) x ≠ x
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
⊢ l ~r l.formPerm.toList x

Tactic:
refine (toList_formPerm_isRotated_self _ ?_ hn _ ?_).symm

Result:
case intro.intro.intro.refine_2.mk.intro.refine_1
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hx : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) x ≠ x
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
⊢ 2 ≤ l.length

case intro.intro.intro.refine_2.mk.intro.refine_2
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hx : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) x ≠ x
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
⊢ x ∈ l

Proof state:
case intro.intro.intro.refine_2.mk.intro.refine_1
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
hx : l.length < 2
⊢ (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) x = x

Tactic:
suffices formPerm l = 1 by simp [this]

Result:
case intro.intro.intro.refine_2.mk.intro.refine_1
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
hx : l.length < 2
⊢ l.formPerm = 1

Proof state:
case intro.intro.intro.refine_2.mk.intro
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hx : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) x ≠ x
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
⊢ Quot.mk (⇑(IsRotated.setoid α)) l = ↑((Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).toList x)

Tactic:
simp only [Cycle.mk_eq_coe, Cycle.coe_eq_coe, Subtype.coe_mk, Cycle.formPerm_coe]

Result:
case intro.intro.intro.refine_2.mk.intro
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
val✝ : Fintype α
x : α
y✝ : Cycle α
l : List α
hn : Cycle.Nodup (Quot.mk (⇑(IsRotated.setoid α)) l)
hf : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).IsCycle
hx : (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) x ≠ x
hy :
  ∀ ⦃y : α⦄,
    (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn) y ≠ y →
      (Cycle.formPerm (Quot.mk (⇑(IsRotated.setoid α)) l) hn).SameCycle x y
⊢ l ~r l.formPerm.toList x

Proof state:
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
f : Perm α
hf : f.IsCycle
⊢ ∃! s, ∃ (h : s.Nodup), s.formPerm h = f

Tactic:
cases nonempty_fintype α

Result:
case intro
α : Type u_1
inst✝¹ : Finite α
inst✝ : DecidableEq α
f : Perm α
hf : f.IsCycle
val✝ : Fintype α
⊢ ∃! s, ∃ (h : s.Nodup), s.formPerm h = f