-- Mathlib/FieldTheory/Finite/GaloisField.lean
theorem finrank {n} (h : n ≠ 0) : Module.finrank (ZMod p) (GaloisField p n) = n

Proof state:
case succ.refine_5
n : ℕ
h : n ≠ 0
n✝ : ℕ
h_prime : Fact (Nat.Prime (n✝ + 1))
this : Fintype (GaloisField (n✝ + 1) n)
g_poly : (ZMod (n✝ + 1))[X] := X ^ (n✝ + 1) ^ n - X
hp : 1 < n✝ + 1
aux : X ^ (n✝ + 1) ^ n - X ≠ 0
key : Fintype.card ↑((X ^ (n✝ + 1) ^ n - X).rootSet (GaloisField (n✝ + 1) n)) = (n✝ + 1) ^ n
nat_degree_eq : (X ^ (n✝ + 1) ^ n - X).natDegree = (n✝ + 1) ^ n
x✝ : GaloisField (n✝ + 1) n
hx✝¹ :
  x✝ ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
x : GaloisField (n✝ + 1) n
hx✝ :
  x ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
hx : x ^ (n✝ + 1) ^ n = x
⊢ (-x) ^ (n✝ + 1) ^ n + x = 0

Tactic:
rw [neg_pow, hx, neg_one_pow_char_pow]

Result:
case succ.refine_5
n : ℕ
h : n ≠ 0
n✝ : ℕ
h_prime : Fact (Nat.Prime (n✝ + 1))
this : Fintype (GaloisField (n✝ + 1) n)
g_poly : (ZMod (n✝ + 1))[X] := X ^ (n✝ + 1) ^ n - X
hp : 1 < n✝ + 1
aux : X ^ (n✝ + 1) ^ n - X ≠ 0
key : Fintype.card ↑((X ^ (n✝ + 1) ^ n - X).rootSet (GaloisField (n✝ + 1) n)) = (n✝ + 1) ^ n
nat_degree_eq : (X ^ (n✝ + 1) ^ n - X).natDegree = (n✝ + 1) ^ n
x✝ : GaloisField (n✝ + 1) n
hx✝¹ :
  x✝ ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
x : GaloisField (n✝ + 1) n
hx✝ :
  x ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
hx : x ^ (n✝ + 1) ^ n = x
⊢ -1 * x + x = 0

Proof state:
case succ.refine_1.inr
n : ℕ
h : n ≠ 0
n✝ : ℕ
h_prime : Fact (Nat.Prime (n✝ + 1))
this : Fintype (GaloisField (n✝ + 1) n)
g_poly : (ZMod (n✝ + 1))[X] := X ^ (n✝ + 1) ^ n - X
hp : 1 < n✝ + 1
aux : X ^ (n✝ + 1) ^ n - X ≠ 0
key : Fintype.card ↑(g_poly.rootSet (GaloisField (n✝ + 1) n)) = (n✝ + 1) ^ n
nat_degree_eq : g_poly.natDegree = (n✝ + 1) ^ n
x✝ : GaloisField (n✝ + 1) n
hx✝ :
  x✝ ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
x : GaloisField (n✝ + 1) n
hx : x ∈ (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField
⊢ (aeval x) (X ^ (n✝ + 1) ^ n - X) = 0

Tactic:
rwa [mem_rootSet_of_ne aux] at hx

Result:
no goals

Proof state:
case succ.refine_1.inl.intro
n : ℕ
h : n ≠ 0
n✝ : ℕ
h_prime : Fact (Nat.Prime (n✝ + 1))
this : Fintype (GaloisField (n✝ + 1) n)
g_poly : (ZMod (n✝ + 1))[X] := X ^ (n✝ + 1) ^ n - X
hp : 1 < n✝ + 1
aux : X ^ (n✝ + 1) ^ n - X ≠ 0
key : Fintype.card ↑(g_poly.rootSet (GaloisField (n✝ + 1) n)) = (n✝ + 1) ^ n
nat_degree_eq : g_poly.natDegree = (n✝ + 1) ^ n
x : GaloisField (n✝ + 1) n
hx :
  x ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
r : ZMod (n✝ + 1)
⊢ (algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) r ^ (n✝ + 1) ^ n -
      (algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) r =
    0

Tactic:
rw [← map_pow, ZMod.pow_card_pow, sub_self]

Result:
no goals

Proof state:
case succ.refine_5
n : ℕ
h : n ≠ 0
n✝ : ℕ
h_prime : Fact (Nat.Prime (n✝ + 1))
this : Fintype (GaloisField (n✝ + 1) n)
g_poly : (ZMod (n✝ + 1))[X] := X ^ (n✝ + 1) ^ n - X
hp : 1 < n✝ + 1
aux : X ^ (n✝ + 1) ^ n - X ≠ 0
key : Fintype.card ↑((X ^ (n✝ + 1) ^ n - X).rootSet (GaloisField (n✝ + 1) n)) = (n✝ + 1) ^ n
nat_degree_eq : (X ^ (n✝ + 1) ^ n - X).natDegree = (n✝ + 1) ^ n
x✝ : GaloisField (n✝ + 1) n
hx✝¹ :
  x✝ ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
x : GaloisField (n✝ + 1) n
hx✝ :
  x ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
hx : x ^ (n✝ + 1) ^ n = x
⊢ -1 * x + x = 0

Tactic:
simp

Result:
no goals

Proof state:
case succ.refine_2
n : ℕ
h : n ≠ 0
n✝ : ℕ
h_prime : Fact (Nat.Prime (n✝ + 1))
this : Fintype (GaloisField (n✝ + 1) n)
g_poly : (ZMod (n✝ + 1))[X] := X ^ (n✝ + 1) ^ n - X
hp : 1 < n✝ + 1
aux : X ^ (n✝ + 1) ^ n - X ≠ 0
key : Fintype.card ↑(g_poly.rootSet (GaloisField (n✝ + 1) n)) = (n✝ + 1) ^ n
nat_degree_eq : g_poly.natDegree = (n✝ + 1) ^ n
x : GaloisField (n✝ + 1) n
hx :
  x ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
⊢ (aeval 0) (X ^ (n✝ + 1) ^ n - X) = 0

Tactic:
rw [← coeff_zero_eq_aeval_zero']

Result:
case succ.refine_2
n : ℕ
h : n ≠ 0
n✝ : ℕ
h_prime : Fact (Nat.Prime (n✝ + 1))
this : Fintype (GaloisField (n✝ + 1) n)
g_poly : (ZMod (n✝ + 1))[X] := X ^ (n✝ + 1) ^ n - X
hp : 1 < n✝ + 1
aux : X ^ (n✝ + 1) ^ n - X ≠ 0
key : Fintype.card ↑(g_poly.rootSet (GaloisField (n✝ + 1) n)) = (n✝ + 1) ^ n
nat_degree_eq : g_poly.natDegree = (n✝ + 1) ^ n
x : GaloisField (n✝ + 1) n
hx :
  x ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
⊢ (algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ((X ^ (n✝ + 1) ^ n - X).coeff 0) = 0

Proof state:
p : ℕ
h_prime : Fact (Nat.Prime p)
n : ℕ
h : n ≠ 0
this : Fintype (GaloisField p n)
g_poly : (ZMod p)[X] := X ^ p ^ n - X
hp : 1 < p
⊢ Module.finrank (ZMod p) (GaloisField p n) = n

Tactic:
have aux : g_poly ≠ 0 := FiniteField.X_pow_card_pow_sub_X_ne_zero _ h hp

Result:
p : ℕ
h_prime : Fact (Nat.Prime p)
n : ℕ
h : n ≠ 0
this : Fintype (GaloisField p n)
g_poly : (ZMod p)[X] := X ^ p ^ n - X
hp : 1 < p
aux : g_poly ≠ 0
⊢ Module.finrank (ZMod p) (GaloisField p n) = n

Proof state:
case succ.refine_2
n : ℕ
h : n ≠ 0
n✝ : ℕ
h_prime : Fact (Nat.Prime (n✝ + 1))
this : Fintype (GaloisField (n✝ + 1) n)
g_poly : (ZMod (n✝ + 1))[X] := X ^ (n✝ + 1) ^ n - X
hp : 1 < n✝ + 1
aux : X ^ (n✝ + 1) ^ n - X ≠ 0
key : Fintype.card ↑(g_poly.rootSet (GaloisField (n✝ + 1) n)) = (n✝ + 1) ^ n
nat_degree_eq : g_poly.natDegree = (n✝ + 1) ^ n
x : GaloisField (n✝ + 1) n
hx :
  x ∈
    Subring.closure
      (Set.range ⇑(algebraMap (ZMod (n✝ + 1)) (GaloisField (n✝ + 1) n)) ∪
        (X ^ (n✝ + 1) ^ n - X).rootSet (X ^ (n✝ + 1) ^ n - X).SplittingField)
hn : 0 = (n✝ + 1) ^ n
⊢ False

Tactic:
exact Nat.not_lt_zero 1 (pow_eq_zero hn.symm ▸ hp)

Result:
no goals