-- Mathlib/NumberTheory/LegendreSymbol/GaussEisensteinLemmas.lean
theorem Ico_map_valMinAbs_natAbs_eq_Ico_map_id (p : ℕ) [hp : Fact p.Prime] (a : ZMod p)
    (hap : a ≠ 0) : ((Ico 1 (p / 2).succ).1.map fun (x : ℕ) => (a * x).valMinAbs.natAbs) =
    (Ico 1 (p / 2).succ).1.map fun a => a

Proof state:
case refine_3
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
⊢ (a * ↑(↑b / a).valMinAbs.natAbs).valMinAbs.natAbs = b

Tactic:
rw [natCast_natAbs_valMinAbs]

Result:
case refine_3
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
⊢ (a * if (↑b / a).val ≤ p / 2 then ↑b / a else -(↑b / a)).valMinAbs.natAbs = b

Proof state:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
⊢ ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ

Tactic:
intro x hx

Result:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
x : ℕ
hx : x ∈ Ico 1 (p / 2).succ
⊢ (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ

Proof state:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
x : ℕ
hx : x ∈ Ico 1 (p / 2).succ
⊢ (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ

Tactic:
simp [hap, CharP.cast_eq_zero_iff (ZMod p) p, hpe hx, Nat.lt_succ_iff, succ_le_iff,
  pos_iff_ne_zero, natAbs_valMinAbs_le _]

Result:
no goals

Proof state:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
⊢ ∀ b ∈ Ico 1 (p / 2).succ, ∃ x, ∃ (_ : x ∈ Ico 1 (p / 2).succ), (a * ↑x).valMinAbs.natAbs = b

Tactic:
intro b hb

Result:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
⊢ ∃ x, ∃ (_ : x ∈ Ico 1 (p / 2).succ), (a * ↑x).valMinAbs.natAbs = b

Proof state:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
⊢ ∃ x, ∃ (_ : x ∈ Ico 1 (p / 2).succ), (a * ↑x).valMinAbs.natAbs = b

Tactic:
refine ⟨(b / a : ZMod p).valMinAbs.natAbs, mem_Ico.mpr ⟨?_, ?_⟩, ?_⟩

Result:
case refine_1
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
⊢ 1 ≤ (↑b / a).valMinAbs.natAbs

case refine_2
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
⊢ (↑b / a).valMinAbs.natAbs < (p / 2).succ

case refine_3
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
⊢ (a * ↑(↑b / a).valMinAbs.natAbs).valMinAbs.natAbs = b

Proof state:
case refine_2.a
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
⊢ (↑b / a).valMinAbs.natAbs ≤ p / 2

Tactic:
apply natAbs_valMinAbs_le

Result:
no goals

Proof state:
case pos
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
h✝ : (↑b / a).val ≤ p / 2
⊢ (a * (↑b / a)).valMinAbs.natAbs = b

Tactic:
rw [mul_div_cancel₀ _ hap, valMinAbs_def_pos, val_cast_of_lt (hep hb),
  if_pos (le_of_lt_succ (mem_Ico.1 hb).2), Int.natAbs_ofNat]

Result:
no goals

Proof state:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
⊢ Multiset.map (fun x => (a * ↑x).valMinAbs.natAbs) (Ico 1 (p / 2).succ).val =
    Multiset.map (fun a => a) (Ico 1 (p / 2).succ).val

Tactic:
have he : ∀ {x}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2 := by
  simp +contextual [Nat.lt_succ_iff, Nat.succ_le_iff, pos_iff_ne_zero]

Result:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
⊢ Multiset.map (fun x => (a * ↑x).valMinAbs.natAbs) (Ico 1 (p / 2).succ).val =
    Multiset.map (fun a => a) (Ico 1 (p / 2).succ).val

Proof state:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
⊢ Multiset.map (fun x => (a * ↑x).valMinAbs.natAbs) (Ico 1 (p / 2).succ).val =
    Multiset.map (fun a => a) (Ico 1 (p / 2).succ).val

Tactic:
have hmem : ∀ (x : ℕ) (_ : x ∈ Ico 1 (p / 2).succ),
    (a * x : ZMod p).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ := by
  intro x hx
  simp [hap, CharP.cast_eq_zero_iff (ZMod p) p, hpe hx, Nat.lt_succ_iff, succ_le_iff,
    pos_iff_ne_zero, natAbs_valMinAbs_le _]

Result:
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
⊢ Multiset.map (fun x => (a * ↑x).valMinAbs.natAbs) (Ico 1 (p / 2).succ).val =
    Multiset.map (fun a => a) (Ico 1 (p / 2).succ).val

Proof state:
case neg
p : ℕ
hp : Fact (Nat.Prime p)
a : ZMod p
hap : a ≠ 0
he : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x ≠ 0 ∧ x ≤ p / 2
hep : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → x < p
hpe : ∀ {x : ℕ}, x ∈ Ico 1 (p / 2).succ → ¬p ∣ x
hmem : ∀ x ∈ Ico 1 (p / 2).succ, (a * ↑x).valMinAbs.natAbs ∈ Ico 1 (p / 2).succ
b : ℕ
hb : b ∈ Ico 1 (p / 2).succ
h✝ : ¬(↑b / a).val ≤ p / 2
⊢ (a * -(↑b / a)).valMinAbs.natAbs = b

Tactic:
rw [mul_neg, mul_div_cancel₀ _ hap, natAbs_valMinAbs_neg, valMinAbs_def_pos,
  val_cast_of_lt (hep hb), if_pos (le_of_lt_succ (mem_Ico.1 hb).2), Int.natAbs_ofNat]

Result:
no goals