l3lab/ntp-mathlib huggingface dataset:
theorem exists_linearIndependent_extension (hs : LinearIndependent K ((↑) : s → V)) (hst : s ⊆ t) :
    ∃ (b : _) (_ : b ⊆ t), s ⊆ b ∧ t ⊆ span K b ∧ LinearIndependent K ((↑) : b → V) := by
  -- Porting note: The placeholder should be solved before `rcases`.
  have := by
    refine zorn_subset_nonempty { b | b ⊆ t ∧ LinearIndependent K ((↑) : b → V) } ?_ _ ⟨hst, hs⟩
    · refine' fun c hc cc _c0 => ⟨⋃₀ c, ⟨_, _⟩, fun x => _⟩
      · 

Proof state:
case refine'_1
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x y z : V
hs : LinearIndependent (ι := { x // x ∈ s }) K Subtype.val
hst : s ⊆ t
c : Set (Set V)
hc : c ⊆ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val}
cc : IsChain (fun x x_1 => x ⊆ x_1) c
_c0 : Set.Nonempty c
⊢ ⋃₀ c ⊆ t

Next tactic:
exact sUnion_subset fun x xc => (hc xc).1
theorem exists_linearIndependent_extension (hs : LinearIndependent K ((↑) : s → V)) (hst : s ⊆ t) :
    ∃ (b : _) (_ : b ⊆ t), s ⊆ b ∧ t ⊆ span K b ∧ LinearIndependent K ((↑) : b → V) := by
  -- Porting note: The placeholder should be solved before `rcases`.
  have := by
    refine zorn_subset_nonempty { b | b ⊆ t ∧ LinearIndependent K ((↑) : b → V) } ?_ _ ⟨hst, hs⟩
    · refine' fun c hc cc _c0 => ⟨⋃₀ c, ⟨_, _⟩, fun x => _⟩
      · exact sUnion_subset fun x xc => (hc xc).1
      · 

Proof state:
case refine'_2
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x y z : V
hs : LinearIndependent (ι := { x // x ∈ s }) K Subtype.val
hst : s ⊆ t
c : Set (Set V)
hc : c ⊆ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val}
cc : IsChain (fun x x_1 => x ⊆ x_1) c
_c0 : Set.Nonempty c
⊢ LinearIndependent (ι := { x // x ∈ ⋃₀ c }) K Subtype.val

Next tactic:
exact linearIndependent_sUnion_of_directed cc.directedOn fun x xc => (hc xc).2
theorem exists_linearIndependent_extension (hs : LinearIndependent K ((↑) : s → V)) (hst : s ⊆ t) :
    ∃ (b : _) (_ : b ⊆ t), s ⊆ b ∧ t ⊆ span K b ∧ LinearIndependent K ((↑) : b → V) := by
  -- Porting note: The placeholder should be solved before `rcases`.
  have := by
    refine zorn_subset_nonempty { b | b ⊆ t ∧ LinearIndependent K ((↑) : b → V) } ?_ _ ⟨hst, hs⟩
    · refine' fun c hc cc _c0 => ⟨⋃₀ c, ⟨_, _⟩, fun x => _⟩
      · exact sUnion_subset fun x xc => (hc xc).1
      · exact linearIndependent_sUnion_of_directed cc.directedOn fun x xc => (hc xc).2
      · 

Proof state:
case refine'_3
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x✝ y z : V
hs : LinearIndependent (ι := { x // x ∈ s }) K Subtype.val
hst : s ⊆ t
c : Set (Set V)
hc : c ⊆ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val}
cc : IsChain (fun x x_1 => x ⊆ x_1) c
_c0 : Set.Nonempty c
x : Set V
⊢ x ∈ c → x ⊆ ⋃₀ c

Next tactic:
exact subset_sUnion_of_mem
theorem exists_linearIndependent_extension (hs : LinearIndependent K ((↑) : s → V)) (hst : s ⊆ t) :
    ∃ (b : _) (_ : b ⊆ t), s ⊆ b ∧ t ⊆ span K b ∧ LinearIndependent K ((↑) : b → V) := by
  -- Porting note: The placeholder should be solved before `rcases`.
  have := by
    refine zorn_subset_nonempty { b | b ⊆ t ∧ LinearIndependent K ((↑) : b → V) } ?_ _ ⟨hst, hs⟩
    · refine' fun c hc cc _c0 => ⟨⋃₀ c, ⟨_, _⟩, fun x => _⟩
      · exact sUnion_subset fun x xc => (hc xc).1
      · exact linearIndependent_sUnion_of_directed cc.directedOn fun x xc => (hc xc).2
      · exact subset_sUnion_of_mem
  

Proof state:
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x y z : V
hs : LinearIndependent (ι := { x // x ∈ s }) K Subtype.val
hst : s ⊆ t
this :
  ∃ m ∈ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val},
    s ⊆ m ∧ ∀ a ∈ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val}, m ⊆ a → a = m
⊢ ∃ b, ∃ (_ : b ⊆ t), s ⊆ b ∧ t ⊆ ↑(span K b) ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val

Next tactic:
rcases this with
    ⟨b, ⟨bt, bi⟩, sb, h⟩
theorem exists_linearIndependent_extension (hs : LinearIndependent K ((↑) : s → V)) (hst : s ⊆ t) :
    ∃ (b : _) (_ : b ⊆ t), s ⊆ b ∧ t ⊆ span K b ∧ LinearIndependent K ((↑) : b → V) := by
  -- Porting note: The placeholder should be solved before `rcases`.
  have := by
    refine zorn_subset_nonempty { b | b ⊆ t ∧ LinearIndependent K ((↑) : b → V) } ?_ _ ⟨hst, hs⟩
    · refine' fun c hc cc _c0 => ⟨⋃₀ c, ⟨_, _⟩, fun x => _⟩
      · exact sUnion_subset fun x xc => (hc xc).1
      · exact linearIndependent_sUnion_of_directed cc.directedOn fun x xc => (hc xc).2
      · exact subset_sUnion_of_mem
  rcases this with
    ⟨b, ⟨bt, bi⟩, sb, h⟩
  · 

Proof state:
case intro.intro.intro.intro
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x y z : V
hs : LinearIndependent (ι := { x // x ∈ s }) K Subtype.val
hst : s ⊆ t
b : Set V
bt : b ⊆ t
bi : LinearIndependent (ι := { x // x ∈ b }) K Subtype.val
sb : s ⊆ b
h : ∀ a ∈ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val}, b ⊆ a → a = b
⊢ ∃ b, ∃ (_ : b ⊆ t), s ⊆ b ∧ t ⊆ ↑(span K b) ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val

Next tactic:
refine' ⟨b, bt, sb, fun x xt => _, bi⟩
theorem exists_linearIndependent_extension (hs : LinearIndependent K ((↑) : s → V)) (hst : s ⊆ t) :
    ∃ (b : _) (_ : b ⊆ t), s ⊆ b ∧ t ⊆ span K b ∧ LinearIndependent K ((↑) : b → V) := by
  -- Porting note: The placeholder should be solved before `rcases`.
  have := by
    refine zorn_subset_nonempty { b | b ⊆ t ∧ LinearIndependent K ((↑) : b → V) } ?_ _ ⟨hst, hs⟩
    · refine' fun c hc cc _c0 => ⟨⋃₀ c, ⟨_, _⟩, fun x => _⟩
      · exact sUnion_subset fun x xc => (hc xc).1
      · exact linearIndependent_sUnion_of_directed cc.directedOn fun x xc => (hc xc).2
      · exact subset_sUnion_of_mem
  rcases this with
    ⟨b, ⟨bt, bi⟩, sb, h⟩
  · refine' ⟨b, bt, sb, fun x xt => _, bi⟩
    

Proof state:
case intro.intro.intro.intro
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x✝ y z : V
hs : LinearIndependent (ι := { x // x ∈ s }) K Subtype.val
hst : s ⊆ t
b : Set V
bt : b ⊆ t
bi : LinearIndependent (ι := { x // x ∈ b }) K Subtype.val
sb : s ⊆ b
h : ∀ a ∈ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val}, b ⊆ a → a = b
x : V
xt : x ∈ t
⊢ x ∈ ↑(span K b)

Next tactic:
by_contra hn
theorem exists_linearIndependent_extension (hs : LinearIndependent K ((↑) : s → V)) (hst : s ⊆ t) :
    ∃ (b : _) (_ : b ⊆ t), s ⊆ b ∧ t ⊆ span K b ∧ LinearIndependent K ((↑) : b → V) := by
  -- Porting note: The placeholder should be solved before `rcases`.
  have := by
    refine zorn_subset_nonempty { b | b ⊆ t ∧ LinearIndependent K ((↑) : b → V) } ?_ _ ⟨hst, hs⟩
    · refine' fun c hc cc _c0 => ⟨⋃₀ c, ⟨_, _⟩, fun x => _⟩
      · exact sUnion_subset fun x xc => (hc xc).1
      · exact linearIndependent_sUnion_of_directed cc.directedOn fun x xc => (hc xc).2
      · exact subset_sUnion_of_mem
  rcases this with
    ⟨b, ⟨bt, bi⟩, sb, h⟩
  · refine' ⟨b, bt, sb, fun x xt => _, bi⟩
    by_contra hn
    

Proof state:
case intro.intro.intro.intro
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x✝ y z : V
hs : LinearIndependent (ι := { x // x ∈ s }) K Subtype.val
hst : s ⊆ t
b : Set V
bt : b ⊆ t
bi : LinearIndependent (ι := { x // x ∈ b }) K Subtype.val
sb : s ⊆ b
h : ∀ a ∈ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val}, b ⊆ a → a = b
x : V
xt : x ∈ t
hn : x ∉ ↑(span K b)
⊢ False

Next tactic:
apply hn
theorem exists_linearIndependent_extension (hs : LinearIndependent K ((↑) : s → V)) (hst : s ⊆ t) :
    ∃ (b : _) (_ : b ⊆ t), s ⊆ b ∧ t ⊆ span K b ∧ LinearIndependent K ((↑) : b → V) := by
  -- Porting note: The placeholder should be solved before `rcases`.
  have := by
    refine zorn_subset_nonempty { b | b ⊆ t ∧ LinearIndependent K ((↑) : b → V) } ?_ _ ⟨hst, hs⟩
    · refine' fun c hc cc _c0 => ⟨⋃₀ c, ⟨_, _⟩, fun x => _⟩
      · exact sUnion_subset fun x xc => (hc xc).1
      · exact linearIndependent_sUnion_of_directed cc.directedOn fun x xc => (hc xc).2
      · exact subset_sUnion_of_mem
  rcases this with
    ⟨b, ⟨bt, bi⟩, sb, h⟩
  · refine' ⟨b, bt, sb, fun x xt => _, bi⟩
    by_contra hn
    apply hn
    

Proof state:
case intro.intro.intro.intro
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x✝ y z : V
hs : LinearIndependent (ι := { x // x ∈ s }) K Subtype.val
hst : s ⊆ t
b : Set V
bt : b ⊆ t
bi : LinearIndependent (ι := { x // x ∈ b }) K Subtype.val
sb : s ⊆ b
h : ∀ a ∈ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val}, b ⊆ a → a = b
x : V
xt : x ∈ t
hn : x ∉ ↑(span K b)
⊢ x ∈ ↑(span K b)

Next tactic:
rw [← h _ ⟨insert_subset_iff.2 ⟨xt, bt⟩, bi.insert hn⟩ (subset_insert _ _)]
theorem exists_linearIndependent_extension (hs : LinearIndependent K ((↑) : s → V)) (hst : s ⊆ t) :
    ∃ (b : _) (_ : b ⊆ t), s ⊆ b ∧ t ⊆ span K b ∧ LinearIndependent K ((↑) : b → V) := by
  -- Porting note: The placeholder should be solved before `rcases`.
  have := by
    refine zorn_subset_nonempty { b | b ⊆ t ∧ LinearIndependent K ((↑) : b → V) } ?_ _ ⟨hst, hs⟩
    · refine' fun c hc cc _c0 => ⟨⋃₀ c, ⟨_, _⟩, fun x => _⟩
      · exact sUnion_subset fun x xc => (hc xc).1
      · exact linearIndependent_sUnion_of_directed cc.directedOn fun x xc => (hc xc).2
      · exact subset_sUnion_of_mem
  rcases this with
    ⟨b, ⟨bt, bi⟩, sb, h⟩
  · refine' ⟨b, bt, sb, fun x xt => _, bi⟩
    by_contra hn
    apply hn
    rw [← h _ ⟨insert_subset_iff.2 ⟨xt, bt⟩, bi.insert hn⟩ (subset_insert _ _)]
    

Proof state:
case intro.intro.intro.intro
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x✝ y z : V
hs : LinearIndependent (ι := { x // x ∈ s }) K Subtype.val
hst : s ⊆ t
b : Set V
bt : b ⊆ t
bi : LinearIndependent (ι := { x // x ∈ b }) K Subtype.val
sb : s ⊆ b
h : ∀ a ∈ {b | b ⊆ t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val}, b ⊆ a → a = b
x : V
xt : x ∈ t
hn : x ∉ ↑(span K b)
⊢ x ∈ ↑(span K (insert x b))

Next tactic:
exact subset_span (mem_insert _ _)
theorem exists_linearIndependent :
    ∃ (b : _) (_ : b ⊆ t), span K b = span K t ∧ LinearIndependent K ((↑) : b → V) := by
  

Proof state:
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x y z : V
⊢ ∃ b, ∃ (_ : b ⊆ t), span K b = span K t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val

Next tactic:
obtain ⟨b, hb₁, -, hb₂, hb₃⟩ :=
    exists_linearIndependent_extension (linearIndependent_empty K V) (Set.empty_subset t)
theorem exists_linearIndependent :
    ∃ (b : _) (_ : b ⊆ t), span K b = span K t ∧ LinearIndependent K ((↑) : b → V) := by
  obtain ⟨b, hb₁, -, hb₂, hb₃⟩ :=
    exists_linearIndependent_extension (linearIndependent_empty K V) (Set.empty_subset t)
  

Proof state:
case intro.intro.intro.intro
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t : Set V
x y z : V
b : Set V
hb₁ : b ⊆ t
hb₂ : t ⊆ ↑(span K b)
hb₃ : LinearIndependent (ι := { x // x ∈ b }) K Subtype.val
⊢ ∃ b, ∃ (_ : b ⊆ t), span K b = span K t ∧ LinearIndependent (ι := { x // x ∈ b }) K Subtype.val

Next tactic:
exact ⟨b, hb₁, (span_eq_of_le _ hb₂ (Submodule.span_mono hb₁)).symm, hb₃⟩
theorem exists_of_linearIndependent_of_finite_span {t : Finset V}
    (hs : LinearIndependent K (fun x => x : s → V)) (hst : s ⊆ (span K ↑t : Submodule K V)) :
    ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = t.card := by
  classical
  have :
    ∀ t : Finset V,
      ∀ s' : Finset V,
        ↑s' ⊆ s →
          s ∩ ↑t = ∅ →
            s ⊆ (span K ↑(s' ∪ t) : Submodule K V) →
              ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = (s' ∪ t).card :=
    fun t =>
    Finset.induction_on t
      (fun s' hs' _ hss' =>
        have : s = ↑s' := eq_of_linearIndependent_of_span_subtype hs hs' <| by 

Proof state:
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t✝¹ : Set V
x y z : V
t✝ : Finset V
hs : LinearIndependent K fun (x : ↑s) => ↑x
hst : s ⊆ ↑(span K ↑t✝)
t s' : Finset V
hs' : ↑s' ⊆ s
x✝ : s ∩ ↑∅ = ∅
hss' : s ⊆ ↑(span K ↑(s' ∪ ∅))
⊢ s ⊆ ↑(span K ↑s')

Next tactic:
simpa using hss'
theorem exists_of_linearIndependent_of_finite_span {t : Finset V}
    (hs : LinearIndependent K (fun x => x : s → V)) (hst : s ⊆ (span K ↑t : Submodule K V)) :
    ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = t.card := by
  classical
  have :
    ∀ t : Finset V,
      ∀ s' : Finset V,
        ↑s' ⊆ s →
          s ∩ ↑t = ∅ →
            s ⊆ (span K ↑(s' ∪ t) : Submodule K V) →
              ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = (s' ∪ t).card :=
    fun t =>
    Finset.induction_on t
      (fun s' hs' _ hss' =>
        have : s = ↑s' := eq_of_linearIndependent_of_span_subtype hs hs' <| by simpa using hss'
        ⟨s', by 

Proof state:
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t✝¹ : Set V
x y z : V
t✝ : Finset V
hs : LinearIndependent K fun (x : ↑s) => ↑x
hst : s ⊆ ↑(span K ↑t✝)
t s' : Finset V
hs' : ↑s' ⊆ s
x✝ : s ∩ ↑∅ = ∅
hss' : s ⊆ ↑(span K ↑(s' ∪ ∅))
this : s = ↑s'
⊢ ↑s' ⊆ s ∪ ↑∅ ∧ s ⊆ ↑s' ∧ Finset.card s' = Finset.card (s' ∪ ∅)

Next tactic:
simp [this]
theorem exists_of_linearIndependent_of_finite_span {t : Finset V}
    (hs : LinearIndependent K (fun x => x : s → V)) (hst : s ⊆ (span K ↑t : Submodule K V)) :
    ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = t.card := by
  classical
  have :
    ∀ t : Finset V,
      ∀ s' : Finset V,
        ↑s' ⊆ s →
          s ∩ ↑t = ∅ →
            s ⊆ (span K ↑(s' ∪ t) : Submodule K V) →
              ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = (s' ∪ t).card :=
    fun t =>
    Finset.induction_on t
      (fun s' hs' _ hss' =>
        have : s = ↑s' := eq_of_linearIndependent_of_span_subtype hs hs' <| by simpa using hss'
        ⟨s', by simp [this]⟩)
      fun b₁ t hb₁t ih s' hs' hst hss' =>
      have hb₁s : b₁ ∉ s := fun h => by
        

Proof state:
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t✝² : Set V
x y z : V
t✝¹ : Finset V
hs : LinearIndependent K fun (x : ↑s) => ↑x
hst✝ : s ⊆ ↑(span K ↑t✝¹)
t✝ : Finset V
b₁ : V
t : Finset V
hb₁t : b₁ ∉ t
ih :
  ∀ (s' : Finset V),
    ↑s' ⊆ s →
      s ∩ ↑t = ∅ → s ⊆ ↑(span K ↑(s' ∪ t)) → ∃ t', ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ Finset.card t' = Finset.card (s' ∪ t)
s' : Finset V
hs' : ↑s' ⊆ s
hst : s ∩ ↑(insert b₁ t) = ∅
hss' : s ⊆ ↑(span K ↑(s' ∪ insert b₁ t))
h : b₁ ∈ s
⊢ False

Next tactic:
have : b₁ ∈ s ∩ ↑(insert b₁ t) := ⟨h, Finset.mem_insert_self _ _⟩
theorem exists_of_linearIndependent_of_finite_span {t : Finset V}
    (hs : LinearIndependent K (fun x => x : s → V)) (hst : s ⊆ (span K ↑t : Submodule K V)) :
    ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = t.card := by
  classical
  have :
    ∀ t : Finset V,
      ∀ s' : Finset V,
        ↑s' ⊆ s →
          s ∩ ↑t = ∅ →
            s ⊆ (span K ↑(s' ∪ t) : Submodule K V) →
              ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = (s' ∪ t).card :=
    fun t =>
    Finset.induction_on t
      (fun s' hs' _ hss' =>
        have : s = ↑s' := eq_of_linearIndependent_of_span_subtype hs hs' <| by simpa using hss'
        ⟨s', by simp [this]⟩)
      fun b₁ t hb₁t ih s' hs' hst hss' =>
      have hb₁s : b₁ ∉ s := fun h => by
        have : b₁ ∈ s ∩ ↑(insert b₁ t) := ⟨h, Finset.mem_insert_self _ _⟩
        

Proof state:
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t✝² : Set V
x y z : V
t✝¹ : Finset V
hs : LinearIndependent K fun (x : ↑s) => ↑x
hst✝ : s ⊆ ↑(span K ↑t✝¹)
t✝ : Finset V
b₁ : V
t : Finset V
hb₁t : b₁ ∉ t
ih :
  ∀ (s' : Finset V),
    ↑s' ⊆ s →
      s ∩ ↑t = ∅ → s ⊆ ↑(span K ↑(s' ∪ t)) → ∃ t', ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ Finset.card t' = Finset.card (s' ∪ t)
s' : Finset V
hs' : ↑s' ⊆ s
hst : s ∩ ↑(insert b₁ t) = ∅
hss' : s ⊆ ↑(span K ↑(s' ∪ insert b₁ t))
h : b₁ ∈ s
this : b₁ ∈ s ∩ ↑(insert b₁ t)
⊢ False

Next tactic:
rwa [hst] at this
theorem exists_of_linearIndependent_of_finite_span {t : Finset V}
    (hs : LinearIndependent K (fun x => x : s → V)) (hst : s ⊆ (span K ↑t : Submodule K V)) :
    ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = t.card := by
  classical
  have :
    ∀ t : Finset V,
      ∀ s' : Finset V,
        ↑s' ⊆ s →
          s ∩ ↑t = ∅ →
            s ⊆ (span K ↑(s' ∪ t) : Submodule K V) →
              ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = (s' ∪ t).card :=
    fun t =>
    Finset.induction_on t
      (fun s' hs' _ hss' =>
        have : s = ↑s' := eq_of_linearIndependent_of_span_subtype hs hs' <| by simpa using hss'
        ⟨s', by simp [this]⟩)
      fun b₁ t hb₁t ih s' hs' hst hss' =>
      have hb₁s : b₁ ∉ s := fun h => by
        have : b₁ ∈ s ∩ ↑(insert b₁ t) := ⟨h, Finset.mem_insert_self _ _⟩
        rwa [hst] at this
      have hb₁s' : b₁ ∉ s' := fun h => hb₁s <| hs' h
      have hst : s ∩ ↑t = ∅ :=
        eq_empty_of_subset_empty <|
          -- Porting note: `-inter_subset_left, -subset_inter_iff` required.
          Subset.trans
            (by 

Proof state:
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t✝² : Set V
x y z : V
t✝¹ : Finset V
hs : LinearIndependent K fun (x : ↑s) => ↑x
hst✝ : s ⊆ ↑(span K ↑t✝¹)
t✝ : Finset V
b₁ : V
t : Finset V
hb₁t : b₁ ∉ t
ih :
  ∀ (s' : Finset V),
    ↑s' ⊆ s →
      s ∩ ↑t = ∅ → s ⊆ ↑(span K ↑(s' ∪ t)) → ∃ t', ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ Finset.card t' = Finset.card (s' ∪ t)
s' : Finset V
hs' : ↑s' ⊆ s
hst : s ∩ ↑(insert b₁ t) = ∅
hss' : s ⊆ ↑(span K ↑(s' ∪ insert b₁ t))
hb₁s : b₁ ∉ s
hb₁s' : b₁ ∉ s'
⊢ s ∩ ↑t ⊆ s ∩ ↑(insert b₁ t)

Next tactic:
simp [inter_subset_inter, Subset.refl, -inter_subset_left, -subset_inter_iff]
theorem exists_of_linearIndependent_of_finite_span {t : Finset V}
    (hs : LinearIndependent K (fun x => x : s → V)) (hst : s ⊆ (span K ↑t : Submodule K V)) :
    ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = t.card := by
  classical
  have :
    ∀ t : Finset V,
      ∀ s' : Finset V,
        ↑s' ⊆ s →
          s ∩ ↑t = ∅ →
            s ⊆ (span K ↑(s' ∪ t) : Submodule K V) →
              ∃ t' : Finset V, ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ t'.card = (s' ∪ t).card :=
    fun t =>
    Finset.induction_on t
      (fun s' hs' _ hss' =>
        have : s = ↑s' := eq_of_linearIndependent_of_span_subtype hs hs' <| by simpa using hss'
        ⟨s', by simp [this]⟩)
      fun b₁ t hb₁t ih s' hs' hst hss' =>
      have hb₁s : b₁ ∉ s := fun h => by
        have : b₁ ∈ s ∩ ↑(insert b₁ t) := ⟨h, Finset.mem_insert_self _ _⟩
        rwa [hst] at this
      have hb₁s' : b₁ ∉ s' := fun h => hb₁s <| hs' h
      have hst : s ∩ ↑t = ∅ :=
        eq_empty_of_subset_empty <|
          -- Porting note: `-inter_subset_left, -subset_inter_iff` required.
          Subset.trans
            (by simp [inter_subset_inter, Subset.refl, -inter_subset_left, -subset_inter_iff])
            (le_of_eq hst)
      Classical.by_cases (p := s ⊆ (span K ↑(s' ∪ t) : Submodule K V))
        (fun this =>
          let ⟨u, hust, hsu, Eq⟩ := ih _ hs' hst this
          have hb₁u : b₁ ∉ u := fun h => (hust h).elim hb₁s hb₁t
          ⟨insert b₁ u, by 

Proof state:
ι : Type u'
ι' : Type u_1
R : Type u_2
K : Type u_3
M : Type u_4
M' : Type u_5
M'' : Type u_6
V : Type u
V' : Type u_7
inst✝⁴ : DivisionRing K
inst✝³ : AddCommGroup V
inst✝² : AddCommGroup V'
inst✝¹ : Module K V
inst✝ : Module K V'
v : ι → V
s t✝² : Set V
x y z : V
t✝¹ : Finset V
hs : LinearIndependent K fun (x : ↑s) => ↑x
hst✝¹ : s ⊆ ↑(span K ↑t✝¹)
t✝ : Finset V
b₁ : V
t : Finset V
hb₁t : b₁ ∉ t
ih :
  ∀ (s' : Finset V),
    ↑s' ⊆ s →
      s ∩ ↑t = ∅ → s ⊆ ↑(span K ↑(s' ∪ t)) → ∃ t', ↑t' ⊆ s ∪ ↑t ∧ s ⊆ ↑t' ∧ Finset.card t' = Finset.card (s' ∪ t)
s' : Finset V
hs' : ↑s' ⊆ s
hst✝ : s ∩ ↑(insert b₁ t) = ∅
hss' : s ⊆ ↑(span K ↑(s' ∪ insert b₁ t))
hb₁s : b₁ ∉ s
hb₁s' : b₁ ∉ s'
hst : s ∩ ↑t = ∅
this : s ⊆ ↑(span K ↑(s' ∪ t))
u : Finset V
hust : ↑u ⊆ s ∪ ↑t
hsu : s ⊆ ↑u
Eq : Finset.card u = Finset.card (s' ∪ t)
hb₁u : b₁ ∉ u
⊢ ↑(insert b₁ u) ⊆ s ∪ ↑(insert b₁ t)

Next tactic:
simp [insert_subset_insert hust]