-- Mathlib/NumberTheory/Transcendental/Liouville/LiouvilleWith.lean
theorem exists_pos (h : LiouvilleWith p x) :
    ∃ (C : ℝ) (_h₀ : 0 < C),
      ∃ᶠ n : ℕ in atTop, 1 ≤ n ∧ ∃ m : ℤ, x ≠ m / n ∧ |x - m / n| < C / n ^ p

Proof state:
case intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
⊢ ∀ (x_1 : ℕ),
    (1 ≤ x_1 ∧ ∃ m, x ≠ ↑m / ↑x_1 ∧ |x - ↑m / ↑x_1| < C / ↑x_1 ^ p) →
      1 ≤ x_1 ∧ ∃ m, x ≠ ↑m / ↑x_1 ∧ |x - ↑m / ↑x_1| < (C ⊔ 1) / ↑x_1 ^ p

Tactic:
rintro n ⟨hle, m, hne, hlt⟩

Result:
case intro.intro.intro.intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
n : ℕ
hle : 1 ≤ n
m : ℤ
hne : x ≠ ↑m / ↑n
hlt : |x - ↑m / ↑n| < C / ↑n ^ p
⊢ 1 ≤ n ∧ ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < (C ⊔ 1) / ↑n ^ p

Proof state:
case intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
⊢ ∃ C, ∃ (_ : 0 < C), ∃ᶠ (n : ℕ) in atTop, 1 ≤ n ∧ ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p

Tactic:
refine ⟨max C 1, zero_lt_one.trans_le <| le_max_right _ _, ?_⟩

Result:
case intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
⊢ ∃ᶠ (n : ℕ) in atTop, 1 ≤ n ∧ ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < (C ⊔ 1) / ↑n ^ p

Proof state:
case intro.intro.intro.intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
n : ℕ
hle : 1 ≤ n
m : ℤ
hne : x ≠ ↑m / ↑n
hlt : |x - ↑m / ↑n| < C / ↑n ^ p
⊢ C / ↑n ^ p ≤ (C ⊔ 1) / ↑n ^ p

Tactic:
gcongr

Result:
case intro.intro.intro.intro.hab
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
n : ℕ
hle : 1 ≤ n
m : ℤ
hne : x ≠ ↑m / ↑n
hlt : |x - ↑m / ↑n| < C / ↑n ^ p
⊢ C ≤ C ⊔ 1

Proof state:
case intro.intro.intro.intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
n : ℕ
hle : 1 ≤ n
m : ℤ
hne : x ≠ ↑m / ↑n
hlt : |x - ↑m / ↑n| < C / ↑n ^ p
⊢ 1 ≤ n ∧ ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < (C ⊔ 1) / ↑n ^ p

Tactic:
refine ⟨hle, m, hne, hlt.trans_le ?_⟩

Result:
case intro.intro.intro.intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
n : ℕ
hle : 1 ≤ n
m : ℤ
hne : x ≠ ↑m / ↑n
hlt : |x - ↑m / ↑n| < C / ↑n ^ p
⊢ C / ↑n ^ p ≤ (C ⊔ 1) / ↑n ^ p

Proof state:
case intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
⊢ ∃ᶠ (n : ℕ) in atTop, 1 ≤ n ∧ ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < (C ⊔ 1) / ↑n ^ p

Tactic:
refine ((eventually_ge_atTop 1).and_frequently hC).mono ?_

Result:
case intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
⊢ ∀ (x_1 : ℕ),
    (1 ≤ x_1 ∧ ∃ m, x ≠ ↑m / ↑x_1 ∧ |x - ↑m / ↑x_1| < C / ↑x_1 ^ p) →
      1 ≤ x_1 ∧ ∃ m, x ≠ ↑m / ↑x_1 ∧ |x - ↑m / ↑x_1| < (C ⊔ 1) / ↑x_1 ^ p

Proof state:
case intro.intro.intro.intro.hab
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
n : ℕ
hle : 1 ≤ n
m : ℤ
hne : x ≠ ↑m / ↑n
hlt : |x - ↑m / ↑n| < C / ↑n ^ p
⊢ C ≤ C ⊔ 1

Tactic:
apply le_max_left

Result:
no goals

Proof state:
p x : ℝ
h : LiouvilleWith p x
⊢ ∃ C, ∃ (_ : 0 < C), ∃ᶠ (n : ℕ) in atTop, 1 ≤ n ∧ ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p

Tactic:
rcases h with ⟨C, hC⟩

Result:
case intro
p x C : ℝ
hC : ∃ᶠ (n : ℕ) in atTop, ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p
⊢ ∃ C, ∃ (_ : 0 < C), ∃ᶠ (n : ℕ) in atTop, 1 ≤ n ∧ ∃ m, x ≠ ↑m / ↑n ∧ |x - ↑m / ↑n| < C / ↑n ^ p