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Description: Baire's Category Theorem. If a nonempty metric space is complete, it is nonmeager in itself. In other words, no open set in the metric space can be the countable union of rare closed subsets (where rare means having a closure with empty interior), so some subset Mk must have a nonempty interior. Theorem 4.7-2 of Kreyszig p. 247. (The terminology "meager" and "nonmeager" is used by Kreyszig to replace Baire's "of the first category" and "of the second category." The latter terms are going out of favor to avoid confusion with category theory.) See bcthlem5 for an overview of the proof. (Contributed by NM, 28-Oct-2007) (Proof shortened by Mario Carneiro, 6-Jan-2014)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | bcth.2 | ⊢ 𝐽 = ( MetOpen ‘ 𝐷 ) | |
| Assertion | bcth | ⊢ ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ∧ ( ( int ‘ 𝐽 ) ‘ ∪ ran 𝑀 ) ≠ ∅ ) → ∃ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) ≠ ∅ ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | bcth.2 | ⊢ 𝐽 = ( MetOpen ‘ 𝐷 ) | |
| 2 | simpll | ⊢ ( ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ) ∧ ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) → 𝐷 ∈ ( CMet ‘ 𝑋 ) ) | |
| 3 | eleq1w | ⊢ ( 𝑥 = 𝑦 → ( 𝑥 ∈ 𝑋 ↔ 𝑦 ∈ 𝑋 ) ) | |
| 4 | eleq1w | ⊢ ( 𝑟 = 𝑚 → ( 𝑟 ∈ ℝ+ ↔ 𝑚 ∈ ℝ+ ) ) | |
| 5 | 3 4 | bi2anan9 | ⊢ ( ( 𝑥 = 𝑦 ∧ 𝑟 = 𝑚 ) → ( ( 𝑥 ∈ 𝑋 ∧ 𝑟 ∈ ℝ+ ) ↔ ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ) ) |
| 6 | simpr | ⊢ ( ( 𝑥 = 𝑦 ∧ 𝑟 = 𝑚 ) → 𝑟 = 𝑚 ) | |
| 7 | 6 | breq1d | ⊢ ( ( 𝑥 = 𝑦 ∧ 𝑟 = 𝑚 ) → ( 𝑟 < ( 1 / 𝑘 ) ↔ 𝑚 < ( 1 / 𝑘 ) ) ) |
| 8 | oveq12 | ⊢ ( ( 𝑥 = 𝑦 ∧ 𝑟 = 𝑚 ) → ( 𝑥 ( ball ‘ 𝐷 ) 𝑟 ) = ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) | |
| 9 | 8 | fveq2d | ⊢ ( ( 𝑥 = 𝑦 ∧ 𝑟 = 𝑚 ) → ( ( cls ‘ 𝐽 ) ‘ ( 𝑥 ( ball ‘ 𝐷 ) 𝑟 ) ) = ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ) |
| 10 | 9 | sseq1d | ⊢ ( ( 𝑥 = 𝑦 ∧ 𝑟 = 𝑚 ) → ( ( ( cls ‘ 𝐽 ) ‘ ( 𝑥 ( ball ‘ 𝐷 ) 𝑟 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ↔ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) |
| 11 | 7 10 | anbi12d | ⊢ ( ( 𝑥 = 𝑦 ∧ 𝑟 = 𝑚 ) → ( ( 𝑟 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑥 ( ball ‘ 𝐷 ) 𝑟 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ↔ ( 𝑚 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) ) |
| 12 | 5 11 | anbi12d | ⊢ ( ( 𝑥 = 𝑦 ∧ 𝑟 = 𝑚 ) → ( ( ( 𝑥 ∈ 𝑋 ∧ 𝑟 ∈ ℝ+ ) ∧ ( 𝑟 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑥 ( ball ‘ 𝐷 ) 𝑟 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) ↔ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) ) ) |
| 13 | 12 | cbvopabv | ⊢ { 〈 𝑥 , 𝑟 〉 ∣ ( ( 𝑥 ∈ 𝑋 ∧ 𝑟 ∈ ℝ+ ) ∧ ( 𝑟 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑥 ( ball ‘ 𝐷 ) 𝑟 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) } = { 〈 𝑦 , 𝑚 〉 ∣ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) } |
| 14 | oveq2 | ⊢ ( 𝑘 = 𝑛 → ( 1 / 𝑘 ) = ( 1 / 𝑛 ) ) | |
| 15 | 14 | breq2d | ⊢ ( 𝑘 = 𝑛 → ( 𝑚 < ( 1 / 𝑘 ) ↔ 𝑚 < ( 1 / 𝑛 ) ) ) |
| 16 | fveq2 | ⊢ ( 𝑘 = 𝑛 → ( 𝑀 ‘ 𝑘 ) = ( 𝑀 ‘ 𝑛 ) ) | |
| 17 | 16 | difeq2d | ⊢ ( 𝑘 = 𝑛 → ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) = ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) |
| 18 | 17 | sseq2d | ⊢ ( 𝑘 = 𝑛 → ( ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ↔ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) |
| 19 | 15 18 | anbi12d | ⊢ ( 𝑘 = 𝑛 → ( ( 𝑚 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ↔ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) ) |
| 20 | 19 | anbi2d | ⊢ ( 𝑘 = 𝑛 → ( ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) ↔ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) ) ) |
| 21 | 20 | opabbidv | ⊢ ( 𝑘 = 𝑛 → { 〈 𝑦 , 𝑚 〉 ∣ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) } = { 〈 𝑦 , 𝑚 〉 ∣ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) } ) |
| 22 | 13 21 | eqtrid | ⊢ ( 𝑘 = 𝑛 → { 〈 𝑥 , 𝑟 〉 ∣ ( ( 𝑥 ∈ 𝑋 ∧ 𝑟 ∈ ℝ+ ) ∧ ( 𝑟 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑥 ( ball ‘ 𝐷 ) 𝑟 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) } = { 〈 𝑦 , 𝑚 〉 ∣ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) } ) |
| 23 | fveq2 | ⊢ ( 𝑧 = 𝑔 → ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) = ( ( ball ‘ 𝐷 ) ‘ 𝑔 ) ) | |
| 24 | 23 | difeq1d | ⊢ ( 𝑧 = 𝑔 → ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) = ( ( ( ball ‘ 𝐷 ) ‘ 𝑔 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) |
| 25 | 24 | sseq2d | ⊢ ( 𝑧 = 𝑔 → ( ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ↔ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑔 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) |
| 26 | 25 | anbi2d | ⊢ ( 𝑧 = 𝑔 → ( ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ↔ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑔 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) ) |
| 27 | 26 | anbi2d | ⊢ ( 𝑧 = 𝑔 → ( ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) ↔ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑔 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) ) ) |
| 28 | 27 | opabbidv | ⊢ ( 𝑧 = 𝑔 → { 〈 𝑦 , 𝑚 〉 ∣ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) } = { 〈 𝑦 , 𝑚 〉 ∣ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑔 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) } ) |
| 29 | 22 28 | cbvmpov | ⊢ ( 𝑘 ∈ ℕ , 𝑧 ∈ ( 𝑋 × ℝ+ ) ↦ { 〈 𝑥 , 𝑟 〉 ∣ ( ( 𝑥 ∈ 𝑋 ∧ 𝑟 ∈ ℝ+ ) ∧ ( 𝑟 < ( 1 / 𝑘 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑥 ( ball ‘ 𝐷 ) 𝑟 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑧 ) ∖ ( 𝑀 ‘ 𝑘 ) ) ) ) } ) = ( 𝑛 ∈ ℕ , 𝑔 ∈ ( 𝑋 × ℝ+ ) ↦ { 〈 𝑦 , 𝑚 〉 ∣ ( ( 𝑦 ∈ 𝑋 ∧ 𝑚 ∈ ℝ+ ) ∧ ( 𝑚 < ( 1 / 𝑛 ) ∧ ( ( cls ‘ 𝐽 ) ‘ ( 𝑦 ( ball ‘ 𝐷 ) 𝑚 ) ) ⊆ ( ( ( ball ‘ 𝐷 ) ‘ 𝑔 ) ∖ ( 𝑀 ‘ 𝑛 ) ) ) ) } ) |
| 30 | simplr | ⊢ ( ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ) ∧ ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) → 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ) | |
| 31 | simpr | ⊢ ( ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ) ∧ ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) → ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) | |
| 32 | 16 | fveqeq2d | ⊢ ( 𝑘 = 𝑛 → ( ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ↔ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑛 ) ) = ∅ ) ) |
| 33 | 32 | cbvralvw | ⊢ ( ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ↔ ∀ 𝑛 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑛 ) ) = ∅ ) |
| 34 | 31 33 | sylib | ⊢ ( ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ) ∧ ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) → ∀ 𝑛 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑛 ) ) = ∅ ) |
| 35 | 1 2 29 30 34 | bcthlem5 | ⊢ ( ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ) ∧ ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) → ( ( int ‘ 𝐽 ) ‘ ∪ ran 𝑀 ) = ∅ ) |
| 36 | 35 | ex | ⊢ ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ) → ( ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ → ( ( int ‘ 𝐽 ) ‘ ∪ ran 𝑀 ) = ∅ ) ) |
| 37 | 36 | necon3ad | ⊢ ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ) → ( ( ( int ‘ 𝐽 ) ‘ ∪ ran 𝑀 ) ≠ ∅ → ¬ ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) ) |
| 38 | 37 | 3impia | ⊢ ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ∧ ( ( int ‘ 𝐽 ) ‘ ∪ ran 𝑀 ) ≠ ∅ ) → ¬ ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) |
| 39 | df-ne | ⊢ ( ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) ≠ ∅ ↔ ¬ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) | |
| 40 | 39 | rexbii | ⊢ ( ∃ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) ≠ ∅ ↔ ∃ 𝑘 ∈ ℕ ¬ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) |
| 41 | rexnal | ⊢ ( ∃ 𝑘 ∈ ℕ ¬ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ↔ ¬ ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) | |
| 42 | 40 41 | bitri | ⊢ ( ∃ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) ≠ ∅ ↔ ¬ ∀ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) = ∅ ) |
| 43 | 38 42 | sylibr | ⊢ ( ( 𝐷 ∈ ( CMet ‘ 𝑋 ) ∧ 𝑀 : ℕ ⟶ ( Clsd ‘ 𝐽 ) ∧ ( ( int ‘ 𝐽 ) ‘ ∪ ran 𝑀 ) ≠ ∅ ) → ∃ 𝑘 ∈ ℕ ( ( int ‘ 𝐽 ) ‘ ( 𝑀 ‘ 𝑘 ) ) ≠ ∅ ) |