-- Mathlib/GroupTheory/Commutator/Basic.lean
theorem commutator_commutator_eq_bot_of_rotate (h1 : ⁅⁅H₂, H₃⁆, H₁⁆ = ⊥) (h2 : ⁅⁅H₃, H₁⁆, H₂⁆ = ⊥) :
    ⁅⁅H₁, H₂⁆, H₃⁆ = ⊥

Proof state:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
⊢ ∀ g₁ ∈ H₁, ∀ g₂ ∈ H₂, ∀ h ∈ ↑H₃, ⁅h, ⁅g₁, g₂⁆⁆ = 1

Tactic:
intro x hx y hy z hz

Result:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
x : G
hx : x ∈ H₁
y : G
hy : y ∈ H₂
z : G
hz : z ∈ ↑H₃
⊢ ⁅z, ⁅x, y⁆⁆ = 1

Proof state:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
x : G
hx : x ∈ H₁
y : G
hy : y ∈ H₂
z : G
hz : z ∈ ↑H₃
⊢ ⁅z, ⁅x, y⁆⁆ = 1

Tactic:
trans x * z * ⁅y, ⁅z⁻¹, x⁻¹⁆⁆⁻¹ * z⁻¹ * y * ⁅x⁻¹, ⁅y⁻¹, z⁆⁆⁻¹ * y⁻¹ * x⁻¹

Result:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
x : G
hx : x ∈ H₁
y : G
hy : y ∈ H₂
z : G
hz : z ∈ ↑H₃
⊢ ⁅z, ⁅x, y⁆⁆ = x * z * ⁅y, ⁅z⁻¹, x⁻¹⁆⁆⁻¹ * z⁻¹ * y * ⁅x⁻¹, ⁅y⁻¹, z⁆⁆⁻¹ * y⁻¹ * x⁻¹

G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
x : G
hx : x ∈ H₁
y : G
hy : y ∈ H₂
z : G
hz : z ∈ ↑H₃
⊢ x * z * ⁅y, ⁅z⁻¹, x⁻¹⁆⁆⁻¹ * z⁻¹ * y * ⁅x⁻¹, ⁅y⁻¹, z⁆⁆⁻¹ * y⁻¹ * x⁻¹ = 1

Proof state:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
x : G
hx : x ∈ H₁
y : G
hy : y ∈ H₂
z : G
hz : z ∈ ↑H₃
⊢ ⁅z, ⁅x, y⁆⁆ = x * z * ⁅y, ⁅z⁻¹, x⁻¹⁆⁆⁻¹ * z⁻¹ * y * ⁅x⁻¹, ⁅y⁻¹, z⁆⁆⁻¹ * y⁻¹ * x⁻¹

Tactic:
simp [commutatorElement_def, mul_assoc]

Result:
no goals

Proof state:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
x : G
hx : x ∈ H₁
y : G
hy : y ∈ H₂
z : G
hz : z ∈ ↑H₃
⊢ x * z * ⁅y, ⁅z⁻¹, x⁻¹⁆⁆⁻¹ * z⁻¹ * y * ⁅x⁻¹, ⁅y⁻¹, z⁆⁆⁻¹ * y⁻¹ * x⁻¹ = 1

Tactic:
rw [h1 _ (H₂.inv_mem hy) _ hz _ (H₁.inv_mem hx), h2 _ (H₃.inv_mem hz) _ (H₁.inv_mem hx) _ hy]

Result:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
x : G
hx : x ∈ H₁
y : G
hy : y ∈ H₂
z : G
hz : z ∈ ↑H₃
⊢ x * z * 1⁻¹ * z⁻¹ * y * 1⁻¹ * y⁻¹ * x⁻¹ = 1

Proof state:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ⁅⁅H₂, H₃⁆, H₁⁆ = ⊥
h2 : ⁅⁅H₃, H₁⁆, H₂⁆ = ⊥
⊢ ⁅⁅H₁, H₂⁆, H₃⁆ = ⊥

Tactic:
simp_rw [commutator_eq_bot_iff_le_centralizer, commutator_le,
  mem_centralizer_iff_commutator_eq_one, ← commutatorElement_def] at h1 h2 ⊢

Result:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
⊢ ∀ g₁ ∈ H₁, ∀ g₂ ∈ H₂, ∀ h ∈ ↑H₃, ⁅h, ⁅g₁, g₂⁆⁆ = 1

Proof state:
G : Type u_1
inst✝ : Group G
H₁ H₂ H₃ : Subgroup G
h1 : ∀ g₁ ∈ H₂, ∀ g₂ ∈ H₃, ∀ h ∈ ↑H₁, ⁅h, ⁅g₁, g₂⁆⁆ = 1
h2 : ∀ g₁ ∈ H₃, ∀ g₂ ∈ H₁, ∀ h ∈ ↑H₂, ⁅h, ⁅g₁, g₂⁆⁆ = 1
x : G
hx : x ∈ H₁
y : G
hy : y ∈ H₂
z : G
hz : z ∈ ↑H₃
⊢ x * z * 1⁻¹ * z⁻¹ * y * 1⁻¹ * y⁻¹ * x⁻¹ = 1

Tactic:
simp [commutatorElement_def, mul_assoc]

Result:
no goals