l3lab/ntp-mathlib huggingface dataset:
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      

Proof state:
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
⊢ x = Function.update x i 1 * Pi.mulSingle i (x i)

Next tactic:
ext j
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      

Proof state:
case h
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
⊢ x j = (Function.update x i 1 * Pi.mulSingle i (x i)) j

Next tactic:
by_cases heq : j = i
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · 

Proof state:
case pos
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
heq : j = i
⊢ x j = (Function.update x i 1 * Pi.mulSingle i (x i)) j

Next tactic:
subst heq
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        

Proof state:
case pos
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
I : Finset η
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
j : η
hnmem : j ∉ I
h1 : ∀ i ∉ insert j I, x i = 1
h2 : ∀ i ∈ insert j I, Pi.mulSingle i (x i) ∈ H
⊢ x j = (Function.update x j 1 * Pi.mulSingle j (x j)) j

Next tactic:
simp
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · 

Proof state:
case neg
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
heq : ¬j = i
⊢ x j = (Function.update x i 1 * Pi.mulSingle i (x i)) j

Next tactic:
simp [heq]
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    

Proof state:
case insert
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
this : x = Function.update x i 1 * Pi.mulSingle i (x i)
⊢ x ∈ H

Next tactic:
rw [this]
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    

Proof state:
case insert
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
this : x = Function.update x i 1 * Pi.mulSingle i (x i)
⊢ Function.update x i 1 * Pi.mulSingle i (x i) ∈ H

Next tactic:
clear this
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    

Proof state:
case insert
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
⊢ Function.update x i 1 * Pi.mulSingle i (x i) ∈ H

Next tactic:
apply mul_mem
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · 

Proof state:
case insert.a
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
⊢ Function.update x i 1 ∈ H

Next tactic:
apply ih
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> 

Proof state:
case insert.a.h1
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
⊢ ∀ i_1 ∉ I, Function.update x i 1 i_1 = 1

Next tactic:
clear ih
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> 

Proof state:
case insert.a.h2
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
ih : ∀ (x : (i : η) → f i), (∀ i ∉ I, x i = 1) → (∀ i ∈ I, Pi.mulSingle i (x i) ∈ H) → x ∈ H
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
⊢ ∀ i_1 ∈ I, Pi.mulSingle i_1 (Function.update x i 1 i_1) ∈ H

Next tactic:
clear ih
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · 

Proof state:
case insert.a.h1
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
⊢ ∀ i_1 ∉ I, Function.update x i 1 i_1 = 1

Next tactic:
intro j hj
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        

Proof state:
case insert.a.h1
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
hj : j ∉ I
⊢ Function.update x i 1 j = 1

Next tactic:
by_cases heq : j = i
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        by_cases heq : j = i
        · 

Proof state:
case pos
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
hj : j ∉ I
heq : j = i
⊢ Function.update x i 1 j = 1

Next tactic:
subst heq
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        by_cases heq : j = i
        · subst heq
          

Proof state:
case pos
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
I : Finset η
x : (i : η) → f i
j : η
hj hnmem : j ∉ I
h1 : ∀ i ∉ insert j I, x i = 1
h2 : ∀ i ∈ insert j I, Pi.mulSingle i (x i) ∈ H
⊢ Function.update x j 1 j = 1

Next tactic:
simp
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        by_cases heq : j = i
        · subst heq
          simp
        · 

Proof state:
case neg
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
hj : j ∉ I
heq : ¬j = i
⊢ Function.update x i 1 j = 1

Next tactic:
simp [heq]
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        by_cases heq : j = i
        · subst heq
          simp
        · simp [heq]
          

Proof state:
case neg
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
hj : j ∉ I
heq : ¬j = i
⊢ x j = 1

Next tactic:
apply h1 j
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        by_cases heq : j = i
        · subst heq
          simp
        · simp [heq]
          apply h1 j
          

Proof state:
case neg
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
hj : j ∉ I
heq : ¬j = i
⊢ j ∉ insert i I

Next tactic:
simpa [heq] using hj
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        by_cases heq : j = i
        · subst heq
          simp
        · simp [heq]
          apply h1 j
          simpa [heq] using hj
      · 

Proof state:
case insert.a.h2
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
⊢ ∀ i_1 ∈ I, Pi.mulSingle i_1 (Function.update x i 1 i_1) ∈ H

Next tactic:
intro j hj
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        by_cases heq : j = i
        · subst heq
          simp
        · simp [heq]
          apply h1 j
          simpa [heq] using hj
      · intro j hj
        

Proof state:
case insert.a.h2
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
hj : j ∈ I
⊢ Pi.mulSingle j (Function.update x i 1 j) ∈ H

Next tactic:
have : j ≠ i := by
          rintro rfl
          contradiction
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        by_cases heq : j = i
        · subst heq
          simp
        · simp [heq]
          apply h1 j
          simpa [heq] using hj
      · intro j hj
        have : j ≠ i := by
          

Proof state:
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
i : η
I : Finset η
hnmem : i ∉ I
x : (i : η) → f i
h1 : ∀ i_1 ∉ insert i I, x i_1 = 1
h2 : ∀ i_1 ∈ insert i I, Pi.mulSingle i_1 (x i_1) ∈ H
j : η
hj : j ∈ I
⊢ j ≠ i

Next tactic:
rintro rfl
@[to_additive]
theorem pi_mem_of_mulSingle_mem_aux [DecidableEq η] (I : Finset η) {H : Subgroup (∀ i, f i)}
    (x : ∀ i, f i) (h1 : ∀ i, i ∉ I → x i = 1) (h2 : ∀ i, i ∈ I → Pi.mulSingle i (x i) ∈ H) :
    x ∈ H := by
  induction' I using Finset.induction_on with i I hnmem ih generalizing x
  · convert one_mem H
    ext i
    exact h1 i (Finset.not_mem_empty i)
  · have : x = Function.update x i 1 * Pi.mulSingle i (x i) := by
      ext j
      by_cases heq : j = i
      · subst heq
        simp
      · simp [heq]
    rw [this]
    clear this
    apply mul_mem
    · apply ih <;> clear ih
      · intro j hj
        by_cases heq : j = i
        · subst heq
          simp
        · simp [heq]
          apply h1 j
          simpa [heq] using hj
      · intro j hj
        have : j ≠ i := by
          rintro rfl
          

Proof state:
G : Type u_1
inst✝³ : Group G
A : Type u_2
inst✝² : AddGroup A
η : Type u_3
f : η → Type u_4
inst✝¹ : (i : η) → Group (f i)
inst✝ : DecidableEq η
H : Subgroup ((i : η) → f i)
I : Finset η
x : (i : η) → f i
j : η
hj : j ∈ I
hnmem : j ∉ I
h1 : ∀ i ∉ insert j I, x i = 1
h2 : ∀ i ∈ insert j I, Pi.mulSingle i (x i) ∈ H
⊢ False

Next tactic:
contradiction