Theorem: CauchySeq.isCauSeq
File: Mathlib/Topology/MetricSpace/CauSeqFilter.lean

Proof steps:
state_before: β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
⊢ IsCauSeq norm f
state_after: case intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
⊢ IsCauSeq norm f
tactic: cases' cauchy_iff.1 hf with hf1 hf2
state_before: case intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
⊢ IsCauSeq norm f
state_after: case intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
⊢ ∃ i, ∀ j ≥ i, ‖f j - f i‖ < ε
tactic: intro ε hε
state_before: case intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
⊢ ∃ i, ∀ j ≥ i, ‖f j - f i‖ < ε
state_after: case intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
ht : t ∈ map f atTop
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
⊢ ∃ i, ∀ j ≥ i, ‖f j - f i‖ < ε
tactic: rcases hf2 { x | dist x.1 x.2 < ε } (dist_mem_uniformity hε) with ⟨t, ⟨ht, htsub⟩⟩
state_before: case intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
ht : t ∈ map f atTop
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
⊢ ∃ i, ∀ j ≥ i, ‖f j - f i‖ < ε
state_after: case intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
ht : ∃ a, ∀ b ≥ a, f b ∈ t
⊢ ∃ i, ∀ j ≥ i, ‖f j - f i‖ < ε
tactic: simp only [mem_map, mem_atTop_sets, mem_preimage] at ht
state_before: case intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
ht : ∃ a, ∀ b ≥ a, f b ∈ t
⊢ ∃ i, ∀ j ≥ i, ‖f j - f i‖ < ε
state_after: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
⊢ ∃ i, ∀ j ≥ i, ‖f j - f i‖ < ε
tactic: cases' ht with N hN
state_before: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
⊢ ∃ i, ∀ j ≥ i, ‖f j - f i‖ < ε
state_after: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
⊢ ∀ j ≥ N, ‖f j - f N‖ < ε
tactic: exists N
state_before: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
⊢ ∀ j ≥ N, ‖f j - f N‖ < ε
state_after: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
j : ℕ
hj : j ≥ N
⊢ ‖f j - f N‖ < ε
tactic: intro j hj
state_before: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
j : ℕ
hj : j ≥ N
⊢ ‖f j - f N‖ < ε
state_after: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
j : ℕ
hj : j ≥ N
⊢ dist (f j) (f N) < ε
tactic: rw [← dist_eq_norm]
state_before: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
j : ℕ
hj : j ≥ N
⊢ dist (f j) (f N) < ε
state_after: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
j : ℕ
hj : j ≥ N
⊢ (f j, f N) ∈ t ×ˢ t
tactic: apply @htsub (f j, f N)
state_before: case intro.intro.intro.intro
β : Type v
inst✝ : NormedField β
f : ℕ → β
hf : CauchySeq f
hf1 : (map f atTop).NeBot
hf2 : ∀ s ∈ uniformity β, ∃ t ∈ map f atTop, t ×ˢ t ⊆ s
ε : ℝ
hε : ε > 0
t : Set β
htsub : t ×ˢ t ⊆ {x | dist x.1 x.2 < ε}
N : ℕ
hN : ∀ b ≥ N, f b ∈ t
j : ℕ
hj : j ≥ N
⊢ (f j, f N) ∈ t ×ˢ t
state_after: no goals
tactic: apply Set.mk_mem_prod <;> solve_by_elim [le_refl]