Module: Mathlib.LinearAlgebra.SymplecticGroup

Goal state before:
pp: l : Type u_1
inst✝² : DecidableEq l
inst✝¹ : Fintype l
R : Type u_3
inst✝ : Field R
A C : Matrix l l R
hker : ∀ (x : l → R), A • x = 0 → C • x = 0 → x = 0
hsymm : Aᵀ * C = Cᵀ * A
V U : Matrix l l R
s : l ≃ Fin C.rank ⊕ Fin (Fintype.card l - C.rank)
hV : IsUnit V
hU : IsUnit U
P : Matrix l l R := V * C * U
heq : P = (fromBlocks 1 0 0 0).submatrix ⇑s ⇑s
P_def : P = V * C * U
Q : Matrix l l R := Vᵀ⁻¹ * A * U
Q_def : Q = Vᵀ⁻¹ * A * U
f : Matrix l l R → Matrix (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) R :=
  fun x ↦ x.submatrix ⇑s.symm ⇑s.symm
hf : ∀ (x : Matrix l l R), f x = x.submatrix ⇑s.symm ⇑s.symm
f_unit : ∀ {x : Matrix l l R}, IsUnit x → IsUnit (f x)
f_mul : ∀ (x y : Matrix l l R), f (x * y) = f x * f y
x✝² : Invertible V
x✝¹ : Invertible U
x✝ : Invertible (f Vᵀ)
x : Fin C.rank ⊕ Fin (Fintype.card l - C.rank) → R
heq1 : (A *ᵥ (f U • x) ∘ ⇑s) ∘ ⇑s.symm = 0
heq2 : (C *ᵥ (f U • x) ∘ ⇑s) ∘ ⇑s.symm = 0
⊢ f U • x = f U • 0

pp: l : Type u_1
inst✝² : DecidableEq l
inst✝¹ : Fintype l
R : Type u_3
inst✝ : Field R
A C : Matrix l l R
hker : ∀ (x : l → R), A • x = 0 → C • x = 0 → x = 0
hsymm : Aᵀ * C = Cᵀ * A
V U : Matrix l l R
s : l ≃ Fin C.rank ⊕ Fin (Fintype.card l - C.rank)
hV : IsUnit V
hU : IsUnit U
P : Matrix l l R := V * C * U
heq : P = (fromBlocks 1 0 0 0).submatrix ⇑s ⇑s
P_def : P = V * C * U
Q : Matrix l l R := Vᵀ⁻¹ * A * U
Q_def : Q = Vᵀ⁻¹ * A * U
f : Matrix l l R → Matrix (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) R :=
  fun x ↦ x.submatrix ⇑s.symm ⇑s.symm
hf : ∀ (x : Matrix l l R), f x = x.submatrix ⇑s.symm ⇑s.symm
f_unit : ∀ {x : Matrix l l R}, IsUnit x → IsUnit (f x)
f_mul : ∀ (x y : Matrix l l R), f (x * y) = f x * f y
x✝² : Invertible V
x✝¹ : Invertible U
x✝ : Invertible (f Vᵀ)
x : Fin C.rank ⊕ Fin (Fintype.card l - C.rank) → R
heq1 : (f A * f U) • x = 0
heq2 : f V • (f C * f U) • x = 0
⊢ IsUnit (f V)

pp: l : Type u_1
inst✝² : DecidableEq l
inst✝¹ : Fintype l
R : Type u_3
inst✝ : Field R
A C : Matrix l l R
hker : ∀ (x : l → R), A • x = 0 → C • x = 0 → x = 0
hsymm : Aᵀ * C = Cᵀ * A
V U : Matrix l l R
s : l ≃ Fin C.rank ⊕ Fin (Fintype.card l - C.rank)
hV : IsUnit V
hU : IsUnit U
P : Matrix l l R := V * C * U
heq : P = (fromBlocks 1 0 0 0).submatrix ⇑s ⇑s
P_def : P = V * C * U
Q : Matrix l l R := Vᵀ⁻¹ * A * U
Q_def : Q = Vᵀ⁻¹ * A * U
f : Matrix l l R → Matrix (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) R :=
  fun x ↦ x.submatrix ⇑s.symm ⇑s.symm
hf : ∀ (x : Matrix l l R), f x = x.submatrix ⇑s.symm ⇑s.symm
f_unit : ∀ {x : Matrix l l R}, IsUnit x → IsUnit (f x)
f_mul : ∀ (x y : Matrix l l R), f (x * y) = f x * f y
x✝² : Invertible V
x✝¹ : Invertible U
x✝ : Invertible (f Vᵀ)
x : Fin C.rank ⊕ Fin (Fintype.card l - C.rank) → R
heq1 : f Vᵀ⁻¹ • (f A * f U) • x = 0
heq2 : f V • (f C * f U) • x = 0
⊢ IsUnit (f Vᵀ⁻¹)

Tactic:
· rw [Equiv.comp_symm_eq, Pi.zero_comp] at heq1 heq2
      exact s.surjective.injective_comp_right <| by simpa using hker _ heq1 heq2

Goal state after:
l : Type u_1
inst✝² : DecidableEq l
inst✝¹ : Fintype l
R : Type u_3
inst✝ : Field R
A C : Matrix l l R
hker : ∀ (x : l → R), A • x = 0 → C • x = 0 → x = 0
hsymm : Aᵀ * C = Cᵀ * A
V U : Matrix l l R
s : l ≃ Fin C.rank ⊕ Fin (Fintype.card l - C.rank)
hV : IsUnit V
hU : IsUnit U
P : Matrix l l R := V * C * U
heq : P = (fromBlocks 1 0 0 0).submatrix ⇑s ⇑s
P_def : P = V * C * U
Q : Matrix l l R := Vᵀ⁻¹ * A * U
Q_def : Q = Vᵀ⁻¹ * A * U
f : Matrix l l R → Matrix (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) R :=
  fun x ↦ x.submatrix ⇑s.symm ⇑s.symm
hf : ∀ (x : Matrix l l R), f x = x.submatrix ⇑s.symm ⇑s.symm
f_unit : ∀ {x : Matrix l l R}, IsUnit x → IsUnit (f x)
f_mul : ∀ (x y : Matrix l l R), f (x * y) = f x * f y
x✝² : Invertible V
x✝¹ : Invertible U
x✝ : Invertible (f Vᵀ)
x : Fin C.rank ⊕ Fin (Fintype.card l - C.rank) → R
heq1 : (f A * f U) • x = 0
heq2 : f V • (f C * f U) • x = 0
⊢ IsUnit (f V)

l : Type u_1
inst✝² : DecidableEq l
inst✝¹ : Fintype l
R : Type u_3
inst✝ : Field R
A C : Matrix l l R
hker : ∀ (x : l → R), A • x = 0 → C • x = 0 → x = 0
hsymm : Aᵀ * C = Cᵀ * A
V U : Matrix l l R
s : l ≃ Fin C.rank ⊕ Fin (Fintype.card l - C.rank)
hV : IsUnit V
hU : IsUnit U
P : Matrix l l R := V * C * U
heq : P = (fromBlocks 1 0 0 0).submatrix ⇑s ⇑s
P_def : P = V * C * U
Q : Matrix l l R := Vᵀ⁻¹ * A * U
Q_def : Q = Vᵀ⁻¹ * A * U
f : Matrix l l R → Matrix (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) (Fin C.rank ⊕ Fin (Fintype.card l - C.rank)) R :=
  fun x ↦ x.submatrix ⇑s.symm ⇑s.symm
hf : ∀ (x : Matrix l l R), f x = x.submatrix ⇑s.symm ⇑s.symm
f_unit : ∀ {x : Matrix l l R}, IsUnit x → IsUnit (f x)
f_mul : ∀ (x y : Matrix l l R), f (x * y) = f x * f y
x✝² : Invertible V
x✝¹ : Invertible U
x✝ : Invertible (f Vᵀ)
x : Fin C.rank ⊕ Fin (Fintype.card l - C.rank) → R
heq1 : f Vᵀ⁻¹ • (f A * f U) • x = 0
heq2 : f V • (f C * f U) • x = 0
⊢ IsUnit (f Vᵀ⁻¹)