l3lab/ntp-mathlib huggingface dataset:
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    

Proof state:
case right
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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
⊢ ∃ a, a ≠ 0 ∧ a • s i ∈ span R (s '' I)

Next tactic:
have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have 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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
⊢ ?m.585572

Next tactic:
refine mt hImaximal ?_
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · 

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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
⊢ ¬I = J

Next tactic:
intro h2
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        

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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h2 : I = J
⊢ False

Next tactic:
rw [h2] at hi
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        

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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
J : Set ι := I ∪ {i}
hi : i ∉ J
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h2 : I = J
⊢ False

Next tactic:
exact absurd hiJ hi
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    

Proof state:
case right
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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
⊢ ∃ a, a ≠ 0 ∧ a • s i ∈ span R (s '' I)

Next tactic:
obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    

Proof state:
case right.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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
f : ι →₀ R
supp_f : f ∈ Finsupp.supported R R J
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
⊢ ∃ a, a ≠ 0 ∧ a • s i ∈ span R (s '' I)

Next tactic:
have hfi : f i ≠ 0 := by
      contrapose hIlinind
      refine' linearDependent_comp_subtype.mpr ⟨f, _, sum_f, f_ne⟩
      simp only [Finsupp.mem_supported, hJ] at supp_f ⊢
      rintro x hx
      refine' (memJ.mp (supp_f hx)).resolve_left _
      rintro rfl
      exact hIlinind (Finsupp.mem_support_iff.mp hx)
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    have hfi : f i ≠ 0 := 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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
f : ι →₀ R
supp_f : f ∈ Finsupp.supported R R J
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
⊢ f i ≠ 0

Next tactic:
contrapose hIlinind
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    have hfi : f i ≠ 0 := by
      contrapose hIlinind
      

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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
f : ι →₀ R
supp_f : f ∈ Finsupp.supported R R J
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
hIlinind : ¬f i ≠ 0
⊢ ¬LinearIndependent R fun (x : ↑I) => s ↑x

Next tactic:
refine' linearDependent_comp_subtype.mpr ⟨f, _, sum_f, f_ne⟩
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    have hfi : f i ≠ 0 := by
      contrapose hIlinind
      refine' linearDependent_comp_subtype.mpr ⟨f, _, sum_f, f_ne⟩
      

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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
f : ι →₀ R
supp_f : f ∈ Finsupp.supported R R J
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
hIlinind : ¬f i ≠ 0
⊢ f ∈ Finsupp.supported R R I

Next tactic:
simp only [Finsupp.mem_supported, hJ] at supp_f ⊢
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    have hfi : f i ≠ 0 := by
      contrapose hIlinind
      refine' linearDependent_comp_subtype.mpr ⟨f, _, sum_f, f_ne⟩
      simp only [Finsupp.mem_supported, hJ] at supp_f ⊢
      

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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
f : ι →₀ R
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
hIlinind : ¬f i ≠ 0
supp_f : ↑f.support ⊆ I ∪ {i}
⊢ ↑f.support ⊆ I

Next tactic:
rintro x hx
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    have hfi : f i ≠ 0 := by
      contrapose hIlinind
      refine' linearDependent_comp_subtype.mpr ⟨f, _, sum_f, f_ne⟩
      simp only [Finsupp.mem_supported, hJ] at supp_f ⊢
      rintro x hx
      

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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x✝ y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
f : ι →₀ R
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
hIlinind : ¬f i ≠ 0
supp_f : ↑f.support ⊆ I ∪ {i}
x : ι
hx : x ∈ ↑f.support
⊢ x ∈ I

Next tactic:
refine' (memJ.mp (supp_f hx)).resolve_left _
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    have hfi : f i ≠ 0 := by
      contrapose hIlinind
      refine' linearDependent_comp_subtype.mpr ⟨f, _, sum_f, f_ne⟩
      simp only [Finsupp.mem_supported, hJ] at supp_f ⊢
      rintro x hx
      refine' (memJ.mp (supp_f hx)).resolve_left _
      

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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x✝ y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
f : ι →₀ R
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
hIlinind : ¬f i ≠ 0
supp_f : ↑f.support ⊆ I ∪ {i}
x : ι
hx : x ∈ ↑f.support
⊢ ¬x = i

Next tactic:
rintro rfl
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    have hfi : f i ≠ 0 := by
      contrapose hIlinind
      refine' linearDependent_comp_subtype.mpr ⟨f, _, sum_f, f_ne⟩
      simp only [Finsupp.mem_supported, hJ] at supp_f ⊢
      rintro x hx
      refine' (memJ.mp (supp_f hx)).resolve_left _
      rintro rfl
      

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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x✝ y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
f : ι →₀ R
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
x : ι
hx : x ∈ ↑f.support
hi : x ∉ I
J : Set ι := I ∪ {x}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {x}
memJ : ∀ {x_1 : ι}, x_1 ∈ J ↔ x_1 = x ∨ x_1 ∈ I
hiJ : x ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
hIlinind : ¬f x ≠ 0
supp_f : ↑f.support ⊆ I ∪ {x}
⊢ False

Next tactic:
exact hIlinind (Finsupp.mem_support_iff.mp hx)
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    have hfi : f i ≠ 0 := by
      contrapose hIlinind
      refine' linearDependent_comp_subtype.mpr ⟨f, _, sum_f, f_ne⟩
      simp only [Finsupp.mem_supported, hJ] at supp_f ⊢
      rintro x hx
      refine' (memJ.mp (supp_f hx)).resolve_left _
      rintro rfl
      exact hIlinind (Finsupp.mem_support_iff.mp hx)
    

Proof state:
case right.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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
f : ι →₀ R
supp_f : f ∈ Finsupp.supported R R J
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
hfi : f i ≠ 0
⊢ ∃ a, a ≠ 0 ∧ a • s i ∈ span R (s '' I)

Next tactic:
use f i, hfi
theorem exists_maximal_independent (s : ι → M) :
    ∃ I : Set ι,
      (LinearIndependent R fun x : I => s x) ∧
        ∀ (i) (_ : i ∉ I), ∃ a : R, a ≠ 0 ∧ a • s i ∈ span R (s '' I) := by
  classical
    rcases exists_maximal_independent' R s with ⟨I, hIlinind, hImaximal⟩
    use I, hIlinind
    intro i hi
    specialize hImaximal (I ∪ {i}) (by simp)
    set J := I ∪ {i} with hJ
    have memJ : ∀ {x}, x ∈ J ↔ x = i ∨ x ∈ I := by simp [hJ]
    have hiJ : i ∈ J := by simp
    have h := by
      refine mt hImaximal ?_
      · intro h2
        rw [h2] at hi
        exact absurd hiJ hi
    obtain ⟨f, supp_f, sum_f, f_ne⟩ := linearDependent_comp_subtype.mp h
    have hfi : f i ≠ 0 := by
      contrapose hIlinind
      refine' linearDependent_comp_subtype.mpr ⟨f, _, sum_f, f_ne⟩
      simp only [Finsupp.mem_supported, hJ] at supp_f ⊢
      rintro x hx
      refine' (memJ.mp (supp_f hx)).resolve_left _
      rintro rfl
      exact hIlinind (Finsupp.mem_support_iff.mp hx)
    use f i, hfi
    

Proof state:
case right
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
v : ι → M
inst✝⁶ : Ring R
inst✝⁵ : AddCommGroup M
inst✝⁴ : AddCommGroup M'
inst✝³ : AddCommGroup M''
inst✝² : Module R M
inst✝¹ : Module R M'
inst✝ : Module R M''
a b : R
x y : M
hv : LinearIndependent R v
s : ι → M
I : Set ι
hIlinind : LinearIndependent R fun (x : ↑I) => s ↑x
i : ι
hi : i ∉ I
J : Set ι := I ∪ {i}
hImaximal : (LinearIndependent R fun (x : ↑J) => s ↑x) → I = J
hJ : J = I ∪ {i}
memJ : ∀ {x : ι}, x ∈ J ↔ x = i ∨ x ∈ I
hiJ : i ∈ J
h : ¬LinearIndependent R fun (x : ↑J) => s ↑x
f : ι →₀ R
supp_f : f ∈ Finsupp.supported R R J
sum_f : ∑ i in f.support, f i • s i = 0
f_ne : f ≠ 0
hfi : f i ≠ 0
⊢ f i • s i ∈ span R (s '' I)

Next tactic:
have hfi' : i ∈ f.support := Finsupp.mem_support_iff.mpr hfi