case mp
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
⊢ sInf s = k + 1 → k + 1 ∈ s ∧ ¬k ∈ s

case mpr
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
⊢ k + 1 ∈ s ∧ ¬k ∈ s → sInf s = k + 1
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
⊢ sInf s = k + 1 ↔ k + 1 ∈ s ∧ ¬k ∈ s
constructor
case mp
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ k + 1 ∈ s ∧ ¬k ∈ s
case mp
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
⊢ sInf s = k + 1 → k + 1 ∈ s ∧ ¬k ∈ s
intro H
case mp
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ k + 1 ≤ k + 1 ∧ ¬k + 1 ≤ k

s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ ℕ

s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ sInf s = ?m.6334 + 1
case mp
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ k + 1 ∈ s ∧ ¬k ∈ s
rw [eq_Ici_of_nonempty_of_upward_closed (nonempty_of_sInf_eq_succ _) hs, H, mem_Ici, mem_Ici]
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ ℕ

s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ sInf s = ?m.6334 + 1
case mp
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ k + 1 ≤ k + 1 ∧ ¬k + 1 ≤ k

s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ ℕ

s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ sInf s = ?m.6334 + 1
exact ⟨le_rfl, k.not_succ_le_self⟩
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ sInf s = k + 1
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ ℕ

s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ sInf s = ?m.6334 + 1
exact k
no goals
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : sInf s = k + 1
⊢ sInf s = k + 1
assumption
case mpr.intro
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : k + 1 ∈ s
H' : ¬k ∈ s
⊢ sInf s = k + 1
case mpr
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
⊢ k + 1 ∈ s ∧ ¬k ∈ s → sInf s = k + 1
rintro ⟨H, H'⟩
case mpr.intro
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : k + 1 ∈ s
H' : ¬k ∈ s
⊢ k + 1 ∈ s ∧ ∀ (n : ℕ), n < k + 1 → ¬n ∈ s
case mpr.intro
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : k + 1 ∈ s
H' : ¬k ∈ s
⊢ sInf s = k + 1
rw [sInf_def (⟨_, H⟩ : s.Nonempty), find_eq_iff]
no goals
case mpr.intro
s : Set ℕ
hs : ∀ (k₁ k₂ : ℕ), k₁ ≤ k₂ → k₁ ∈ s → k₂ ∈ s
k : ℕ
H : k + 1 ∈ s
H' : ¬k ∈ s
⊢ k + 1 ∈ s ∧ ∀ (n : ℕ), n < k + 1 → ¬n ∈ s
exact ⟨H, fun n hnk hns ↦ H' <| hs n k (lt_succ_iff.mp hnk) hns⟩