-- Mathlib/Analysis/Asymptotics/TVS.lean
lemma isLittleOTVS_one [ContinuousSMul 𝕜 E] : f =o[𝕜;l] (1 : α → 𝕜) ↔ Tendsto f l (𝓝 0)

Proof state:
case mpr
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf : Tendsto f l (𝓝 0)
U : Set E
hU : U ∈ 𝓝 0
ε : ℝ≥0
hε : ε ≠ 0
⊢ ∀ᶠ (x : α) in l, egauge 𝕜 U (f x) ≤ ↑ε * egauge 𝕜 (ball 0 1) (1 x)

Tactic:
rcases NormedField.exists_norm_lt 𝕜 hε.bot_lt with ⟨c, hc₀, hcε⟩

Result:
case mpr.intro.intro
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf : Tendsto f l (𝓝 0)
U : Set E
hU : U ∈ 𝓝 0
ε : ℝ≥0
hε : ε ≠ 0
c : 𝕜
hc₀ : 0 < ‖c‖
hcε : ‖c‖ < (fun a => ↑a) ε
⊢ ∀ᶠ (x : α) in l, egauge 𝕜 U (f x) ≤ ↑ε * egauge 𝕜 (ball 0 1) (1 x)

Proof state:
case mp
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf :
  ∀ i ∈ 𝓝 0, ∃ j, 0 < j ∧ ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id i) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 j) (1 x)
⊢ Tendsto f l (𝓝 0)

Tactic:
rw [(nhds_basis_balanced 𝕜 E).tendsto_right_iff]

Result:
case mp
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf :
  ∀ i ∈ 𝓝 0, ∃ j, 0 < j ∧ ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id i) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 j) (1 x)
⊢ ∀ (i : Set E), i ∈ 𝓝 0 ∧ Balanced 𝕜 i → ∀ᶠ (x : α) in l, f x ∈ id i

Proof state:
case mpr
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
⊢ Tendsto f l (𝓝 0) → f =o[𝕜;l] 1

Tactic:
intro hf U hU

Result:
case mpr
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf : Tendsto f l (𝓝 0)
U : Set E
hU : U ∈ 𝓝 0
⊢ ∃ V ∈ 𝓝 0, ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 U (f x) ≤ ↑ε * egauge 𝕜 V (1 x)

Proof state:
case funProp.discharger
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf :
  ∀ i ∈ 𝓝 0, ∃ j, 0 < j ∧ ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id i) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 j) (1 x)
U : Set E
hU : U ∈ 𝓝 0
hUb : Balanced 𝕜 U
r : ℝ≥0
hr : ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id U) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 ↑r) (1 x)
hr₀ : 0 < r
c : 𝕜
hc : 1 < ‖c‖
⊢ ↑‖c‖₊ ≠ ⊤

Tactic:
first | apply ENNReal.coe_ne_top | positivity

Result:
no goals

Proof state:
case mpr
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf : Tendsto f l (𝓝 0)
U : Set E
hU : U ∈ 𝓝 0
⊢ ∃ V ∈ 𝓝 0, ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 U (f x) ≤ ↑ε * egauge 𝕜 V (1 x)

Tactic:
refine ⟨ball 0 1, ball_mem_nhds _ one_pos, fun ε hε ↦ ?_⟩

Result:
case mpr
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf : Tendsto f l (𝓝 0)
U : Set E
hU : U ∈ 𝓝 0
ε : ℝ≥0
hε : ε ≠ 0
⊢ ∀ᶠ (x : α) in l, egauge 𝕜 U (f x) ≤ ↑ε * egauge 𝕜 (ball 0 1) (1 x)

Proof state:
case mp.intro.intro.intro.intro.intro.intro.intro
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf :
  ∀ i ∈ 𝓝 0, ∃ j, 0 < j ∧ ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id i) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 j) (1 x)
U : Set E
hU : U ∈ 𝓝 0
hUb : Balanced 𝕜 U
r : ℝ≥0
hr : ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id U) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 ↑r) (1 x)
hr₀ : 0 < r
c : 𝕜
hc : 1 < ‖c‖
ε : ℝ≥0
hε₀ : 0 < ε
hε : ↑ε * ↑‖c‖₊ / ↑r < 1
⊢ ∀ᶠ (x : α) in l, f x ∈ id U

Tactic:
filter_upwards [hr ε hε₀.ne'] with x hx

Result:
case h
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf :
  ∀ i ∈ 𝓝 0, ∃ j, 0 < j ∧ ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id i) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 j) (1 x)
U : Set E
hU : U ∈ 𝓝 0
hUb : Balanced 𝕜 U
r : ℝ≥0
hr : ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id U) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 ↑r) (1 x)
hr₀ : 0 < r
c : 𝕜
hc : 1 < ‖c‖
ε : ℝ≥0
hε₀ : 0 < ε
hε : ↑ε * ↑‖c‖₊ / ↑r < 1
x : α
hx : egauge 𝕜 (id U) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 ↑r) (1 x)
⊢ f x ∈ id U

Proof state:
case mp.intro.intro.intro.intro.intro
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf :
  ∀ i ∈ 𝓝 0, ∃ j, 0 < j ∧ ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id i) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 j) (1 x)
U : Set E
hU : U ∈ 𝓝 0
hUb : Balanced 𝕜 U
r : ℝ≥0
hr : ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id U) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 ↑r) (1 x)
hr₀ : 0 < r
c : 𝕜
hc : 1 < ‖c‖
⊢ ∀ᶠ (x : α) in l, f x ∈ id U

Tactic:
obtain ⟨ε, hε₀, hε⟩ : ∃ ε : ℝ≥0, 0 < ε ∧ (ε * ‖c‖₊ / r : ℝ≥0∞) < 1 := by
  apply Eventually.exists_gt
  refine Continuous.tendsto' ?_ _ _ (by simp) |>.eventually_lt_const zero_lt_one
  fun_prop (disch := intros; first | apply ENNReal.coe_ne_top | positivity)

Result:
case mp.intro.intro.intro.intro.intro.intro.intro
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf :
  ∀ i ∈ 𝓝 0, ∃ j, 0 < j ∧ ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id i) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 j) (1 x)
U : Set E
hU : U ∈ 𝓝 0
hUb : Balanced 𝕜 U
r : ℝ≥0
hr : ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id U) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 ↑r) (1 x)
hr₀ : 0 < r
c : 𝕜
hc : 1 < ‖c‖
ε : ℝ≥0
hε₀ : 0 < ε
hε : ↑ε * ↑‖c‖₊ / ↑r < 1
⊢ ∀ᶠ (x : α) in l, f x ∈ id U

Proof state:
case funProp.discharger
α : Type u_1
𝕜 : Type u_3
E : Type u_4
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : AddCommGroup E
inst✝² : TopologicalSpace E
inst✝¹ : Module 𝕜 E
l : Filter α
f : α → E
inst✝ : ContinuousSMul 𝕜 E
hf :
  ∀ i ∈ 𝓝 0, ∃ j, 0 < j ∧ ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id i) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 j) (1 x)
U : Set E
hU : U ∈ 𝓝 0
hUb : Balanced 𝕜 U
r : ℝ≥0
hr : ∀ (ε : ℝ≥0), ε ≠ 0 → ∀ᶠ (x : α) in l, egauge 𝕜 (id U) (f x) ≤ ↑ε * egauge 𝕜 (ball 0 ↑r) (1 x)
hr₀ : 0 < r
c : 𝕜
hc : 1 < ‖c‖
⊢ ↑r ≠ 0

Tactic:
positivity

Result:
no goals