-- Mathlib/Analysis/NormedSpace/OperatorNorm/Basic.lean
private lemma uniformity_eq_seminorm :
    𝓤 (E →SL[σ₁₂] F) = ⨅ r > 0, 𝓟 {f | ‖f.1 - f.2‖ < r}

Proof state:
case refine_2
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
x✝¹ : Set E × ℝ
s : Set E
r : ℝ
x✝ : IsVonNBounded 𝕜 (s, r).1 ∧ 0 < (s, r).2
hs : IsVonNBounded 𝕜 (s, r).1
hr : 0 < (s, r).2
⊢ ∃ r_1 > 0, ContinuousLinearMap.seminorm.ball 0 r_1 ⊆ {f | ∀ x ∈ (s, r).1, f x ∈ closedBall 0 (s, r).2}

Tactic:
rcases (NormedSpace.isVonNBounded_iff' _).1 hs with ⟨ε, hε⟩

Result:
case refine_2.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
x✝¹ : Set E × ℝ
s : Set E
r : ℝ
x✝ : IsVonNBounded 𝕜 (s, r).1 ∧ 0 < (s, r).2
hs : IsVonNBounded 𝕜 (s, r).1
hr : 0 < (s, r).2
ε : ℝ
hε : ∀ x ∈ (s, r).1, ‖x‖ ≤ ε
⊢ ∃ r_1 > 0, ContinuousLinearMap.seminorm.ball 0 r_1 ⊆ {f | ∀ x ∈ (s, r).1, f x ∈ closedBall 0 (s, r).2}

Proof state:
case refine_2.intro.intro.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
x✝¹ : Set E × ℝ
s : Set E
r : ℝ
x✝ : IsVonNBounded 𝕜 (s, r).1 ∧ 0 < (s, r).2
hs : IsVonNBounded 𝕜 (s, r).1
hr : 0 < (s, r).2
ε : ℝ
hε : ∀ x ∈ (s, r).1, ‖x‖ ≤ ε
δ : ℝ
hδ₀ : 0 < δ
hδ : ε * δ < (s, r).2
⊢ ∃ r_1 > 0, ContinuousLinearMap.seminorm.ball 0 r_1 ⊆ {f | ∀ x ∈ (s, r).1, f x ∈ closedBall 0 (s, r).2}

Tactic:
refine ⟨δ, hδ₀, fun f hf x hx ↦ ?_⟩

Result:
case refine_2.intro.intro.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
x✝¹ : Set E × ℝ
s : Set E
r : ℝ
x✝ : IsVonNBounded 𝕜 (s, r).1 ∧ 0 < (s, r).2
hs : IsVonNBounded 𝕜 (s, r).1
hr : 0 < (s, r).2
ε : ℝ
hε : ∀ x ∈ (s, r).1, ‖x‖ ≤ ε
δ : ℝ
hδ₀ : 0 < δ
hδ : ε * δ < (s, r).2
f : E →SL[σ₁₂] F
hf : f ∈ ContinuousLinearMap.seminorm.ball 0 δ
x : E
hx : x ∈ (s, r).1
⊢ f x ∈ closedBall 0 (s, r).2

Proof state:
case refine_1.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
c : 𝕜
hc : 1 < ‖c‖
f : E →SL[σ₁₂] F
hf : ∀ (x : E), ‖x‖ ≤ 1 → ‖f x‖ ≤ 1
⊢ ‖f‖ ≤ ‖c‖

Tactic:
refine opNorm_le_of_shell (f := f) one_pos (norm_nonneg c) hc fun x hcx hx ↦ ?_

Result:
case refine_1.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
c : 𝕜
hc : 1 < ‖c‖
f : E →SL[σ₁₂] F
hf : ∀ (x : E), ‖x‖ ≤ 1 → ‖f x‖ ≤ 1
x : E
hcx : 1 / ‖c‖ ≤ ‖x‖
hx : ‖x‖ < 1
⊢ ‖f x‖ ≤ ‖c‖ * ‖x‖

Proof state:
case refine_2.intro.intro.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
x✝¹ : Set E × ℝ
s : Set E
r : ℝ
x✝ : IsVonNBounded 𝕜 (s, r).1 ∧ 0 < (s, r).2
hs : IsVonNBounded 𝕜 (s, r).1
hr : 0 < (s, r).2
ε : ℝ
hε : ∀ x ∈ (s, r).1, ‖x‖ ≤ ε
δ : ℝ
hδ₀ : 0 < δ
hδ : δ * ε < (s, r).2
f : E →SL[σ₁₂] F
x : E
hx : x ∈ (s, r).1
hf : ContinuousLinearMap.seminorm f < δ
⊢ ‖f x‖ ≤ r

Tactic:
exact le_trans (le_of_opNorm_le_of_le _ hf.le (hε _ hx)) hδ.le

Result:
no goals

Proof state:
case refine_1.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
c : 𝕜
hc : 1 < ‖c‖
⊢ ∃ r, ContinuousLinearMap.seminorm.closedBall 0 r ∈ 𝓝 0

Tactic:
refine ⟨‖c‖, ContinuousLinearMap.hasBasis_nhds_zero.mem_iff.2
  ⟨(closedBall 0 1, closedBall 0 1), ?_⟩⟩

Result:
case refine_1.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
c : 𝕜
hc : 1 < ‖c‖
⊢ (IsVonNBounded 𝕜 (closedBall 0 1, closedBall 0 1).1 ∧ (closedBall 0 1, closedBall 0 1).2 ∈ 𝓝 0) ∧
    {f | ∀ x ∈ (closedBall 0 1, closedBall 0 1).1, f x ∈ (closedBall 0 1, closedBall 0 1).2} ⊆
      ContinuousLinearMap.seminorm.closedBall 0 ‖c‖

Proof state:
case refine_2.intro.intro.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
x✝¹ : Set E × ℝ
s : Set E
r : ℝ
x✝ : IsVonNBounded 𝕜 (s, r).1 ∧ 0 < (s, r).2
hs : IsVonNBounded 𝕜 (s, r).1
hr : 0 < (s, r).2
ε : ℝ
hε : ∀ x ∈ (s, r).1, ‖x‖ ≤ ε
δ : ℝ
hδ₀ : 0 < δ
hδ : ε * δ < (s, r).2
f : E →SL[σ₁₂] F
x : E
hx : x ∈ (s, r).1
hf : ContinuousLinearMap.seminorm f < δ
⊢ ‖f x‖ ≤ r

Tactic:
rw [mul_comm] at hδ

Result:
case refine_2.intro.intro.intro
𝕜 : Type u_1
𝕜₂ : Type u_2
E : Type u_4
F : Type u_5
inst✝⁶ : SeminormedAddCommGroup E
inst✝⁵ : SeminormedAddCommGroup F
inst✝⁴ : NontriviallyNormedField 𝕜
inst✝³ : NontriviallyNormedField 𝕜₂
inst✝² : NormedSpace 𝕜 E
inst✝¹ : NormedSpace 𝕜₂ F
σ₁₂ : 𝕜 →+* 𝕜₂
inst✝ : RingHomIsometric σ₁₂
x✝¹ : Set E × ℝ
s : Set E
r : ℝ
x✝ : IsVonNBounded 𝕜 (s, r).1 ∧ 0 < (s, r).2
hs : IsVonNBounded 𝕜 (s, r).1
hr : 0 < (s, r).2
ε : ℝ
hε : ∀ x ∈ (s, r).1, ‖x‖ ≤ ε
δ : ℝ
hδ₀ : 0 < δ
hδ : δ * ε < (s, r).2
f : E →SL[σ₁₂] F
x : E
hx : x ∈ (s, r).1
hf : ContinuousLinearMap.seminorm f < δ
⊢ ‖f x‖ ≤ r