Theorem: IsCauSeq.bounded
File: Mathlib/Algebra/Order/CauSeq/Basic.lean

Proof steps:
state_before: α : Type u_1
β : Type u_2
inst✝² : LinearOrderedField α
inst✝¹ : Ring β
abv : β → α
inst✝ : IsAbsoluteValue abv
f g : ℕ → β
hf : IsCauSeq abv f
⊢ ∃ r, ∀ (i : ℕ), abv (f i) < r
state_after: case intro
α : Type u_1
β : Type u_2
inst✝² : LinearOrderedField α
inst✝¹ : Ring β
abv : β → α
inst✝ : IsAbsoluteValue abv
f g : ℕ → β
hf : IsCauSeq abv f
i : ℕ
h : ∀ j ≥ i, abv (f j - f i) < 1
⊢ ∃ r, ∀ (i : ℕ), abv (f i) < r
tactic: obtain ⟨i, h⟩ := hf _ zero_lt_one
state_before: case intro
α : Type u_1
β : Type u_2
inst✝² : LinearOrderedField α
inst✝¹ : Ring β
abv : β → α
inst✝ : IsAbsoluteValue abv
f g : ℕ → β
hf : IsCauSeq abv f
i : ℕ
h : ∀ j ≥ i, abv (f j - f i) < 1
⊢ ∃ r, ∀ (i : ℕ), abv (f i) < r
state_after: case intro
α : Type u_1
β : Type u_2
inst✝² : LinearOrderedField α
inst✝¹ : Ring β
abv : β → α
inst✝ : IsAbsoluteValue abv
f g : ℕ → β
hf : IsCauSeq abv f
i : ℕ
h : ∀ j ≥ i, abv (f j - f i) < 1
R : ℕ → α := Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
hR : R = Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
⊢ ∃ r, ∀ (i : ℕ), abv (f i) < r
tactic: set R : ℕ → α := @Nat.rec (fun _ => α) (abv (f 0)) fun i c => max c (abv (f i.succ)) with hR
state_before: case intro
α : Type u_1
β : Type u_2
inst✝² : LinearOrderedField α
inst✝¹ : Ring β
abv : β → α
inst✝ : IsAbsoluteValue abv
f g : ℕ → β
hf : IsCauSeq abv f
i : ℕ
h : ∀ j ≥ i, abv (f j - f i) < 1
R : ℕ → α := Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
hR : R = Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
this : ∀ (i j : ℕ), j ≤ i → abv (f j) ≤ R i
⊢ ∃ r, ∀ (i : ℕ), abv (f i) < r
state_after: case intro
α : Type u_1
β : Type u_2
inst✝² : LinearOrderedField α
inst✝¹ : Ring β
abv : β → α
inst✝ : IsAbsoluteValue abv
f g : ℕ → β
hf : IsCauSeq abv f
i : ℕ
h : ∀ j ≥ i, abv (f j - f i) < 1
R : ℕ → α := Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
hR : R = Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
this : ∀ (i j : ℕ), j ≤ i → abv (f j) ≤ R i
j : ℕ
⊢ abv (f j) < R i + 1
tactic: refine ⟨R i + 1, fun j ↦ ?_⟩
state_before: case intro
α : Type u_1
β : Type u_2
inst✝² : LinearOrderedField α
inst✝¹ : Ring β
abv : β → α
inst✝ : IsAbsoluteValue abv
f g : ℕ → β
hf : IsCauSeq abv f
i : ℕ
h : ∀ j ≥ i, abv (f j - f i) < 1
R : ℕ → α := Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
hR : R = Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
this : ∀ (i j : ℕ), j ≤ i → abv (f j) ≤ R i
j : ℕ
⊢ abv (f j) < R i + 1
state_after: case intro.inl
α : Type u_1
β : Type u_2
inst✝² : LinearOrderedField α
inst✝¹ : Ring β
abv : β → α
inst✝ : IsAbsoluteValue abv
f g : ℕ → β
hf : IsCauSeq abv f
i : ℕ
h : ∀ j ≥ i, abv (f j - f i) < 1
R : ℕ → α := Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
hR : R = Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
this : ∀ (i j : ℕ), j ≤ i → abv (f j) ≤ R i
j : ℕ
hji : j ≤ i
⊢ abv (f j) < R i + 1

case intro.inr
α : Type u_1
β : Type u_2
inst✝² : LinearOrderedField α
inst✝¹ : Ring β
abv : β → α
inst✝ : IsAbsoluteValue abv
f g : ℕ → β
hf : IsCauSeq abv f
i : ℕ
h : ∀ j ≥ i, abv (f j - f i) < 1
R : ℕ → α := Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
hR : R = Nat.rec (abv (f 0)) fun i c => max c (abv (f i.succ))
this : ∀ (i j : ℕ), j ≤ i → abv (f j) ≤ R i
j : ℕ
hij : i ≤ j
⊢ abv (f j) < R i + 1
tactic: obtain hji | hij := le_total j i