Theorem: Matrix.Pivot.exists_isTwoBlockDiagonal_of_ne_zero
File: Mathlib/LinearAlgebra/Matrix/Transvection.lean

Proof steps:
state_before: n : Type u_1
p : Type u_2
R : Type u₂
𝕜 : Type u_3
inst✝³ : Field 𝕜
inst✝² : DecidableEq n
inst✝¹ : DecidableEq p
inst✝ : CommRing R
r : ℕ
M : Matrix (Fin r ⊕ Unit) (Fin r ⊕ Unit) 𝕜
hM : M (inr ()) (inr ()) ≠ 0
⊢ ∃ L L', ((List.map toMatrix L).prod * M * (List.map toMatrix L').prod).IsTwoBlockDiagonal
state_after: n : Type u_1
p : Type u_2
R : Type u₂
𝕜 : Type u_3
inst✝³ : Field 𝕜
inst✝² : DecidableEq n
inst✝¹ : DecidableEq p
inst✝ : CommRing R
r : ℕ
M : Matrix (Fin r ⊕ Unit) (Fin r ⊕ Unit) 𝕜
hM : M (inr ()) (inr ()) ≠ 0
L : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inl i, j := inr (), hij := ⋯, c := -M (inl i) (inr ()) / M (inr ()) (inr ()) }
⊢ ∃ L L', ((List.map toMatrix L).prod * M * (List.map toMatrix L').prod).IsTwoBlockDiagonal
tactic: let L : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
    List.ofFn fun i : Fin r =>
      ⟨inl i, inr unit, by simp, -M (inl i) (inr unit) / M (inr unit) (inr unit)⟩
state_before: n : Type u_1
p : Type u_2
R : Type u₂
𝕜 : Type u_3
inst✝³ : Field 𝕜
inst✝² : DecidableEq n
inst✝¹ : DecidableEq p
inst✝ : CommRing R
r : ℕ
M : Matrix (Fin r ⊕ Unit) (Fin r ⊕ Unit) 𝕜
hM : M (inr ()) (inr ()) ≠ 0
L : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inl i, j := inr (), hij := ⋯, c := -M (inl i) (inr ()) / M (inr ()) (inr ()) }
⊢ ∃ L L', ((List.map toMatrix L).prod * M * (List.map toMatrix L').prod).IsTwoBlockDiagonal
state_after: n : Type u_1
p : Type u_2
R : Type u₂
𝕜 : Type u_3
inst✝³ : Field 𝕜
inst✝² : DecidableEq n
inst✝¹ : DecidableEq p
inst✝ : CommRing R
r : ℕ
M : Matrix (Fin r ⊕ Unit) (Fin r ⊕ Unit) 𝕜
hM : M (inr ()) (inr ()) ≠ 0
L : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inl i, j := inr (), hij := ⋯, c := -M (inl i) (inr ()) / M (inr ()) (inr ()) }
L' : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inr (), j := inl i, hij := ⋯, c := -M (inr ()) (inl i) / M (inr ()) (inr ()) }
⊢ ∃ L L', ((List.map toMatrix L).prod * M * (List.map toMatrix L').prod).IsTwoBlockDiagonal
tactic: let L' : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
    List.ofFn fun i : Fin r =>
      ⟨inr unit, inl i, by simp, -M (inr unit) (inl i) / M (inr unit) (inr unit)⟩
state_before: n : Type u_1
p : Type u_2
R : Type u₂
𝕜 : Type u_3
inst✝³ : Field 𝕜
inst✝² : DecidableEq n
inst✝¹ : DecidableEq p
inst✝ : CommRing R
r : ℕ
M : Matrix (Fin r ⊕ Unit) (Fin r ⊕ Unit) 𝕜
hM : M (inr ()) (inr ()) ≠ 0
L : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inl i, j := inr (), hij := ⋯, c := -M (inl i) (inr ()) / M (inr ()) (inr ()) }
L' : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inr (), j := inl i, hij := ⋯, c := -M (inr ()) (inl i) / M (inr ()) (inr ()) }
⊢ ∃ L L', ((List.map toMatrix L).prod * M * (List.map toMatrix L').prod).IsTwoBlockDiagonal
state_after: n : Type u_1
p : Type u_2
R : Type u₂
𝕜 : Type u_3
inst✝³ : Field 𝕜
inst✝² : DecidableEq n
inst✝¹ : DecidableEq p
inst✝ : CommRing R
r : ℕ
M : Matrix (Fin r ⊕ Unit) (Fin r ⊕ Unit) 𝕜
hM : M (inr ()) (inr ()) ≠ 0
L : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inl i, j := inr (), hij := ⋯, c := -M (inl i) (inr ()) / M (inr ()) (inr ()) }
L' : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inr (), j := inl i, hij := ⋯, c := -M (inr ()) (inl i) / M (inr ()) (inr ()) }
⊢ ((List.map toMatrix L).prod * M * (List.map toMatrix L').prod).IsTwoBlockDiagonal
tactic: refine ⟨L, L', ?_⟩
state_before: n : Type u_1
p : Type u_2
R : Type u₂
𝕜 : Type u_3
inst✝³ : Field 𝕜
inst✝² : DecidableEq n
inst✝¹ : DecidableEq p
inst✝ : CommRing R
r : ℕ
M : Matrix (Fin r ⊕ Unit) (Fin r ⊕ Unit) 𝕜
hM : M (inr ()) (inr ()) ≠ 0
L : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inl i, j := inr (), hij := ⋯, c := -M (inl i) (inr ()) / M (inr ()) (inr ()) }
L' : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inr (), j := inl i, hij := ⋯, c := -M (inr ()) (inl i) / M (inr ()) (inr ()) }
A : List.map toMatrix L = listTransvecCol M
B : List.map toMatrix L' = listTransvecRow M
⊢ ((List.map toMatrix L).prod * M * (List.map toMatrix L').prod).IsTwoBlockDiagonal
state_after: n : Type u_1
p : Type u_2
R : Type u₂
𝕜 : Type u_3
inst✝³ : Field 𝕜
inst✝² : DecidableEq n
inst✝¹ : DecidableEq p
inst✝ : CommRing R
r : ℕ
M : Matrix (Fin r ⊕ Unit) (Fin r ⊕ Unit) 𝕜
hM : M (inr ()) (inr ()) ≠ 0
L : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inl i, j := inr (), hij := ⋯, c := -M (inl i) (inr ()) / M (inr ()) (inr ()) }
L' : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inr (), j := inl i, hij := ⋯, c := -M (inr ()) (inl i) / M (inr ()) (inr ()) }
A : List.map toMatrix L = listTransvecCol M
B : List.map toMatrix L' = listTransvecRow M
⊢ ((listTransvecCol M).prod * M * (listTransvecRow M).prod).IsTwoBlockDiagonal
tactic: rw [A, B]
state_before: n : Type u_1
p : Type u_2
R : Type u₂
𝕜 : Type u_3
inst✝³ : Field 𝕜
inst✝² : DecidableEq n
inst✝¹ : DecidableEq p
inst✝ : CommRing R
r : ℕ
M : Matrix (Fin r ⊕ Unit) (Fin r ⊕ Unit) 𝕜
hM : M (inr ()) (inr ()) ≠ 0
L : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inl i, j := inr (), hij := ⋯, c := -M (inl i) (inr ()) / M (inr ()) (inr ()) }
L' : List (TransvectionStruct (Fin r ⊕ Unit) 𝕜) :=
  List.ofFn fun i => { i := inr (), j := inl i, hij := ⋯, c := -M (inr ()) (inl i) / M (inr ()) (inr ()) }
A : List.map toMatrix L = listTransvecCol M
B : List.map toMatrix L' = listTransvecRow M
⊢ ((listTransvecCol M).prod * M * (listTransvecRow M).prod).IsTwoBlockDiagonal
state_after: no goals
tactic: exact isTwoBlockDiagonal_listTransvecCol_mul_mul_listTransvecRow M hM