Theorem: IsCompactOperator.continuous
File: Mathlib/Analysis/NormedSpace/CompactOperator.lean

tactic: letI : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace _
state_before: 𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
hf : IsCompactOperator ↑f
⊢ Continuous ↑f

tactic: haveI : UniformAddGroup M₂ := comm_topologicalAddGroup_is_uniform
state_before: 𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
hf : IsCompactOperator ↑f
this : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
⊢ Continuous ↑f

tactic: refine' continuous_of_continuousAt_zero f fun U hU => _
state_before: 𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
hf : IsCompactOperator ↑f
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
⊢ Continuous ↑f

tactic: rw [map_zero] at hU
state_before: 𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
hf : IsCompactOperator ↑f
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 (↑f 0)
⊢ U ∈ map (↑f) (𝓝 0)

tactic: rcases hf with ⟨K, hK, hKf⟩
state_before: 𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
hf : IsCompactOperator ↑f
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
⊢ U ∈ map (↑f) (𝓝 0)

tactic: rcases hK.totallyBounded.isVonNBounded 𝕜₂ hU with ⟨r, hr, hrU⟩
state_before: case intro.intro
𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
⊢ U ∈ map (↑f) (𝓝 0)

tactic: rcases NormedField.exists_lt_norm 𝕜₁ r with ⟨c, hc⟩
state_before: case intro.intro.intro.intro
𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
⊢ U ∈ map (↑f) (𝓝 0)

tactic: have hcnz : c ≠ 0 := ne_zero_of_norm_ne_zero (hr.trans hc).ne.symm
state_before: case intro.intro.intro.intro.intro
𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
c : 𝕜₁
hc : r < ‖c‖
⊢ U ∈ map (↑f) (𝓝 0)

tactic: suffices (σ₁₂ <| c⁻¹) • K ⊆ U by
  refine' mem_of_superset _ this
  have : IsUnit c⁻¹ := hcnz.isUnit.inv
  rwa [mem_map, preimage_smul_setₛₗ _ _ _ f this, set_smul_mem_nhds_zero_iff (inv_ne_zero hcnz)]
state_before: case intro.intro.intro.intro.intro
𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
c : 𝕜₁
hc : r < ‖c‖
hcnz : c ≠ 0
⊢ U ∈ map (↑f) (𝓝 0)

tactic: rw [map_inv₀, ← subset_set_smul_iff₀ ((map_ne_zero σ₁₂).mpr hcnz)]
state_before: case intro.intro.intro.intro.intro
𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
c : 𝕜₁
hc : r < ‖c‖
hcnz : c ≠ 0
⊢ ↑σ₁₂ c⁻¹ • K ⊆ U

tactic: refine' hrU (σ₁₂ c) _
state_before: case intro.intro.intro.intro.intro
𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
c : 𝕜₁
hc : r < ‖c‖
hcnz : c ≠ 0
⊢ K ⊆ ↑σ₁₂ c • U

tactic: rw [RingHomIsometric.is_iso]
state_before: case intro.intro.intro.intro.intro
𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
c : 𝕜₁
hc : r < ‖c‖
hcnz : c ≠ 0
⊢ r ≤ ‖↑σ₁₂ c‖

tactic: exact hc.le
state_before: case intro.intro.intro.intro.intro
𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
c : 𝕜₁
hc : r < ‖c‖
hcnz : c ≠ 0
⊢ r ≤ ‖c‖

tactic: refine' mem_of_superset _ this
state_before: 𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝¹ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this✝ : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
c : 𝕜₁
hc : r < ‖c‖
hcnz : c ≠ 0
this : ↑σ₁₂ c⁻¹ • K ⊆ U
⊢ U ∈ map (↑f) (𝓝 0)

tactic: have : IsUnit c⁻¹ := hcnz.isUnit.inv
state_before: 𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝¹ : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this✝ : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
c : 𝕜₁
hc : r < ‖c‖
hcnz : c ≠ 0
this : ↑σ₁₂ c⁻¹ • K ⊆ U
⊢ ↑σ₁₂ c⁻¹ • K ∈ map (↑f) (𝓝 0)

tactic: rwa [mem_map, preimage_smul_setₛₗ _ _ _ f this, set_smul_mem_nhds_zero_iff (inv_ne_zero hcnz)]
state_before: 𝕜₁ : Type u_1
𝕜₂ : Type u_2
inst✝¹² : NontriviallyNormedField 𝕜₁
inst✝¹¹ : NontriviallyNormedField 𝕜₂
σ₁₂ : 𝕜₁ →+* 𝕜₂
inst✝¹⁰ : RingHomIsometric σ₁₂
M₁ : Type u_3
M₂ : Type u_4
inst✝⁹ : TopologicalSpace M₁
inst✝⁸ : AddCommGroup M₁
inst✝⁷ : TopologicalSpace M₂
inst✝⁶ : AddCommGroup M₂
inst✝⁵ : Module 𝕜₁ M₁
inst✝⁴ : Module 𝕜₂ M₂
inst✝³ : TopologicalAddGroup M₁
inst✝² : ContinuousConstSMul 𝕜₁ M₁
inst✝¹ : TopologicalAddGroup M₂
inst✝ : ContinuousSMul 𝕜₂ M₂
f : M₁ →ₛₗ[σ₁₂] M₂
this✝² : UniformSpace M₂ := TopologicalAddGroup.toUniformSpace M₂
this✝¹ : UniformAddGroup M₂
U : Set M₂
hU : U ∈ 𝓝 0
K : Set M₂
hK : IsCompact K
hKf : ↑f ⁻¹' K ∈ 𝓝 0
r : ℝ
hr : 0 < r
hrU : ∀ (a : 𝕜₂), r ≤ ‖a‖ → K ⊆ a • U
c : 𝕜₁
hc : r < ‖c‖
hcnz : c ≠ 0
this✝ : ↑σ₁₂ c⁻¹ • K ⊆ U
this : IsUnit c⁻¹
⊢ ↑σ₁₂ c⁻¹ • K ∈ map (↑f) (𝓝 0)