-- Mathlib/LinearAlgebra/Matrix/ZPow.lean
theorem pow_inv_comm' (A : M) (m n : ℕ) : A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m

Proof state:
case succ
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
⊢ A⁻¹ ^ m * A ^ (n + 1) = A ^ (n + 1) * A⁻¹ ^ m

Tactic:
rcases m with m | m

Result:
case succ.zero
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
⊢ A⁻¹ ^ 0 * A ^ (n + 1) = A ^ (n + 1) * A⁻¹ ^ 0

case succ.succ
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
⊢ A⁻¹ ^ (m + 1) * A ^ (n + 1) = A ^ (n + 1) * A⁻¹ ^ (m + 1)

Proof state:
case succ.succ
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
⊢ A⁻¹ ^ (m + 1) * A ^ (n + 1) = A ^ (n + 1) * A⁻¹ ^ (m + 1)

Tactic:
rcases nonsing_inv_cancel_or_zero A with ⟨h, h'⟩ | h

Result:
case succ.succ.inl.intro
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
h : A⁻¹ * A = 1
h' : A * A⁻¹ = 1
⊢ A⁻¹ ^ (m + 1) * A ^ (n + 1) = A ^ (n + 1) * A⁻¹ ^ (m + 1)

case succ.succ.inr
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
h : A⁻¹ = 0
⊢ A⁻¹ ^ (m + 1) * A ^ (n + 1) = A ^ (n + 1) * A⁻¹ ^ (m + 1)

Proof state:
case succ.succ.inl.intro
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
h : A⁻¹ * A = 1
h' : A * A⁻¹ = 1
⊢ A⁻¹ ^ (m + 1) * A ^ (n + 1) = A ^ (n + 1) * A⁻¹ ^ (m + 1)

Tactic:
calc
  A⁻¹ ^ (m + 1) * A ^ (n + 1) = A⁻¹ ^ m * (A⁻¹ * A) * A ^ n := by
    simp only [pow_succ A⁻¹, pow_succ' A, Matrix.mul_assoc]
  _ = A ^ n * A⁻¹ ^ m := by simp only [h, Matrix.mul_one, Matrix.one_mul, IH m]
  _ = A ^ n * (A * A⁻¹) * A⁻¹ ^ m := by simp only [h', Matrix.mul_one, Matrix.one_mul]
  _ = A ^ (n + 1) * A⁻¹ ^ (m + 1) := by
    simp only [pow_succ A, pow_succ' A⁻¹, Matrix.mul_assoc]

Result:
no goals

Proof state:
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
h : A⁻¹ * A = 1
h' : A * A⁻¹ = 1
⊢ A ^ n * (A * A⁻¹) * A⁻¹ ^ m = A ^ (n + 1) * A⁻¹ ^ (m + 1)

Tactic:
simp only [pow_succ A, pow_succ' A⁻¹, Matrix.mul_assoc]

Result:
no goals

Proof state:
case succ.succ.inr
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
h : A⁻¹ = 0
⊢ A⁻¹ ^ (m + 1) * A ^ (n + 1) = A ^ (n + 1) * A⁻¹ ^ (m + 1)

Tactic:
simp [h]

Result:
no goals

Proof state:
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
h : A⁻¹ * A = 1
h' : A * A⁻¹ = 1
⊢ A⁻¹ ^ (m + 1) * A ^ (n + 1) = A⁻¹ ^ m * (A⁻¹ * A) * A ^ n

Tactic:
simp only [pow_succ A⁻¹, pow_succ' A, Matrix.mul_assoc]

Result:
no goals

Proof state:
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
h : A⁻¹ * A = 1
h' : A * A⁻¹ = 1
⊢ A ^ n * A⁻¹ ^ m = A ^ n * (A * A⁻¹) * A⁻¹ ^ m

Tactic:
simp only [h', Matrix.mul_one, Matrix.one_mul]

Result:
no goals

Proof state:
case zero
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
m : ℕ
⊢ A⁻¹ ^ m * A ^ 0 = A ^ 0 * A⁻¹ ^ m

Tactic:
simp

Result:
no goals

Proof state:
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
m : ℕ
h : A⁻¹ * A = 1
h' : A * A⁻¹ = 1
⊢ A⁻¹ ^ m * (A⁻¹ * A) * A ^ n = A ^ n * A⁻¹ ^ m

Tactic:
simp only [h, Matrix.mul_one, Matrix.one_mul, IH m]

Result:
no goals

Proof state:
case succ.zero
n' : Type u_1
inst✝² : DecidableEq n'
inst✝¹ : Fintype n'
R : Type u_2
inst✝ : CommRing R
A : M
n : ℕ
IH : ∀ (m : ℕ), A⁻¹ ^ m * A ^ n = A ^ n * A⁻¹ ^ m
⊢ A⁻¹ ^ 0 * A ^ (n + 1) = A ^ (n + 1) * A⁻¹ ^ 0

Tactic:
simp

Result:
no goals