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Description: Rewrite a countable union as a disjoint union. (Contributed by Mario Carneiro, 20-Mar-2014)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | iundisj.1 | ⊢ ( 𝑛 = 𝑘 → 𝐴 = 𝐵 ) | |
| Assertion | iundisj | ⊢ ∪ 𝑛 ∈ ℕ 𝐴 = ∪ 𝑛 ∈ ℕ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | iundisj.1 | ⊢ ( 𝑛 = 𝑘 → 𝐴 = 𝐵 ) | |
| 2 | ssrab2 | ⊢ { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ⊆ ℕ | |
| 3 | nnuz | ⊢ ℕ = ( ℤ≥ ‘ 1 ) | |
| 4 | 2 3 | sseqtri | ⊢ { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ⊆ ( ℤ≥ ‘ 1 ) |
| 5 | rabn0 | ⊢ ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ≠ ∅ ↔ ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ) | |
| 6 | 5 | biimpri | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ≠ ∅ ) |
| 7 | infssuzcl | ⊢ ( ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ⊆ ( ℤ≥ ‘ 1 ) ∧ { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ≠ ∅ ) → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ∈ { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ) | |
| 8 | 4 6 7 | sylancr | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ∈ { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ) |
| 9 | nfrab1 | ⊢ Ⅎ 𝑛 { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } | |
| 10 | nfcv | ⊢ Ⅎ 𝑛 ℝ | |
| 11 | nfcv | ⊢ Ⅎ 𝑛 < | |
| 12 | 9 10 11 | nfinf | ⊢ Ⅎ 𝑛 inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) |
| 13 | nfcv | ⊢ Ⅎ 𝑛 ℕ | |
| 14 | 12 | nfcsb1 | ⊢ Ⅎ 𝑛 ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 |
| 15 | 14 | nfcri | ⊢ Ⅎ 𝑛 𝑥 ∈ ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 |
| 16 | csbeq1a | ⊢ ( 𝑛 = inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) → 𝐴 = ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ) | |
| 17 | 16 | eleq2d | ⊢ ( 𝑛 = inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) → ( 𝑥 ∈ 𝐴 ↔ 𝑥 ∈ ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ) ) |
| 18 | 12 13 15 17 | elrabf | ⊢ ( inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ∈ { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ↔ ( inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ∈ ℕ ∧ 𝑥 ∈ ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ) ) |
| 19 | 8 18 | sylib | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → ( inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ∈ ℕ ∧ 𝑥 ∈ ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ) ) |
| 20 | 19 | simpld | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ∈ ℕ ) |
| 21 | 19 | simprd | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → 𝑥 ∈ ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ) |
| 22 | 20 | nnred | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ∈ ℝ ) |
| 23 | 22 | ltnrd | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → ¬ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) < inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) |
| 24 | eliun | ⊢ ( 𝑥 ∈ ∪ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝐵 ↔ ∃ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝑥 ∈ 𝐵 ) | |
| 25 | 22 | ad2antrr | ⊢ ( ( ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ∧ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) ∧ 𝑥 ∈ 𝐵 ) → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ∈ ℝ ) |
| 26 | elfzouz | ⊢ ( 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) → 𝑘 ∈ ( ℤ≥ ‘ 1 ) ) | |
| 27 | 26 3 | eleqtrrdi | ⊢ ( 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) → 𝑘 ∈ ℕ ) |
| 28 | 27 | ad2antlr | ⊢ ( ( ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ∧ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) ∧ 𝑥 ∈ 𝐵 ) → 𝑘 ∈ ℕ ) |
| 29 | 28 | nnred | ⊢ ( ( ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ∧ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) ∧ 𝑥 ∈ 𝐵 ) → 𝑘 ∈ ℝ ) |
| 30 | 1 | eleq2d | ⊢ ( 𝑛 = 𝑘 → ( 𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵 ) ) |
| 31 | simpr | ⊢ ( ( ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ∧ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) ∧ 𝑥 ∈ 𝐵 ) → 𝑥 ∈ 𝐵 ) | |
| 32 | 30 28 31 | elrabd | ⊢ ( ( ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ∧ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) ∧ 𝑥 ∈ 𝐵 ) → 𝑘 ∈ { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ) |
| 33 | infssuzle | ⊢ ( ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ⊆ ( ℤ≥ ‘ 1 ) ∧ 𝑘 ∈ { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } ) → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ≤ 𝑘 ) | |
| 34 | 4 32 33 | sylancr | ⊢ ( ( ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ∧ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) ∧ 𝑥 ∈ 𝐵 ) → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ≤ 𝑘 ) |
| 35 | elfzolt2 | ⊢ ( 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) → 𝑘 < inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) | |
| 36 | 35 | ad2antlr | ⊢ ( ( ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ∧ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) ∧ 𝑥 ∈ 𝐵 ) → 𝑘 < inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) |
| 37 | 25 29 25 34 36 | lelttrd | ⊢ ( ( ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ∧ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) ∧ 𝑥 ∈ 𝐵 ) → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) < inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) |
| 38 | 37 | rexlimdva2 | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → ( ∃ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝑥 ∈ 𝐵 → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) < inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) |
| 39 | 24 38 | biimtrid | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → ( 𝑥 ∈ ∪ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝐵 → inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) < inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) |
| 40 | 23 39 | mtod | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → ¬ 𝑥 ∈ ∪ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝐵 ) |
| 41 | 21 40 | eldifd | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → 𝑥 ∈ ( ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝐵 ) ) |
| 42 | csbeq1 | ⊢ ( 𝑚 = inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) → ⦋ 𝑚 / 𝑛 ⦌ 𝐴 = ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ) | |
| 43 | oveq2 | ⊢ ( 𝑚 = inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) → ( 1 ..^ 𝑚 ) = ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) ) | |
| 44 | 43 | iuneq1d | ⊢ ( 𝑚 = inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) → ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 = ∪ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝐵 ) |
| 45 | 42 44 | difeq12d | ⊢ ( 𝑚 = inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) → ( ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) = ( ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝐵 ) ) |
| 46 | 45 | eleq2d | ⊢ ( 𝑚 = inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) → ( 𝑥 ∈ ( ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) ↔ 𝑥 ∈ ( ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝐵 ) ) ) |
| 47 | 46 | rspcev | ⊢ ( ( inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ∈ ℕ ∧ 𝑥 ∈ ( ⦋ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ inf ( { 𝑛 ∈ ℕ ∣ 𝑥 ∈ 𝐴 } , ℝ , < ) ) 𝐵 ) ) → ∃ 𝑚 ∈ ℕ 𝑥 ∈ ( ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) ) |
| 48 | 20 41 47 | syl2anc | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → ∃ 𝑚 ∈ ℕ 𝑥 ∈ ( ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) ) |
| 49 | nfv | ⊢ Ⅎ 𝑚 𝑥 ∈ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) | |
| 50 | nfcsb1v | ⊢ Ⅎ 𝑛 ⦋ 𝑚 / 𝑛 ⦌ 𝐴 | |
| 51 | nfcv | ⊢ Ⅎ 𝑛 ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 | |
| 52 | 50 51 | nfdif | ⊢ Ⅎ 𝑛 ( ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) |
| 53 | 52 | nfcri | ⊢ Ⅎ 𝑛 𝑥 ∈ ( ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) |
| 54 | csbeq1a | ⊢ ( 𝑛 = 𝑚 → 𝐴 = ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ) | |
| 55 | oveq2 | ⊢ ( 𝑛 = 𝑚 → ( 1 ..^ 𝑛 ) = ( 1 ..^ 𝑚 ) ) | |
| 56 | 55 | iuneq1d | ⊢ ( 𝑛 = 𝑚 → ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 = ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) |
| 57 | 54 56 | difeq12d | ⊢ ( 𝑛 = 𝑚 → ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) = ( ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) ) |
| 58 | 57 | eleq2d | ⊢ ( 𝑛 = 𝑚 → ( 𝑥 ∈ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) ↔ 𝑥 ∈ ( ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) ) ) |
| 59 | 49 53 58 | cbvrexw | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) ↔ ∃ 𝑚 ∈ ℕ 𝑥 ∈ ( ⦋ 𝑚 / 𝑛 ⦌ 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑚 ) 𝐵 ) ) |
| 60 | 48 59 | sylibr | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 → ∃ 𝑛 ∈ ℕ 𝑥 ∈ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) ) |
| 61 | eldifi | ⊢ ( 𝑥 ∈ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) → 𝑥 ∈ 𝐴 ) | |
| 62 | 61 | reximi | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) → ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ) |
| 63 | 60 62 | impbii | ⊢ ( ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ↔ ∃ 𝑛 ∈ ℕ 𝑥 ∈ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) ) |
| 64 | eliun | ⊢ ( 𝑥 ∈ ∪ 𝑛 ∈ ℕ 𝐴 ↔ ∃ 𝑛 ∈ ℕ 𝑥 ∈ 𝐴 ) | |
| 65 | eliun | ⊢ ( 𝑥 ∈ ∪ 𝑛 ∈ ℕ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) ↔ ∃ 𝑛 ∈ ℕ 𝑥 ∈ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) ) | |
| 66 | 63 64 65 | 3bitr4i | ⊢ ( 𝑥 ∈ ∪ 𝑛 ∈ ℕ 𝐴 ↔ 𝑥 ∈ ∪ 𝑛 ∈ ℕ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) ) |
| 67 | 66 | eqriv | ⊢ ∪ 𝑛 ∈ ℕ 𝐴 = ∪ 𝑛 ∈ ℕ ( 𝐴 ∖ ∪ 𝑘 ∈ ( 1 ..^ 𝑛 ) 𝐵 ) |