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Description: Conditions for the trace of a filter base F to be a filter base. (Contributed by Mario Carneiro, 13-Oct-2015)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | trfbas2 | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( ( 𝐹 ↾t 𝐴 ) ∈ ( fBas ‘ 𝐴 ) ↔ ¬ ∅ ∈ ( 𝐹 ↾t 𝐴 ) ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | elfvdm | ⊢ ( 𝐹 ∈ ( fBas ‘ 𝑌 ) → 𝑌 ∈ dom fBas ) | |
| 2 | ssexg | ⊢ ( ( 𝐴 ⊆ 𝑌 ∧ 𝑌 ∈ dom fBas ) → 𝐴 ∈ V ) | |
| 3 | 2 | ancoms | ⊢ ( ( 𝑌 ∈ dom fBas ∧ 𝐴 ⊆ 𝑌 ) → 𝐴 ∈ V ) |
| 4 | 1 3 | sylan | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → 𝐴 ∈ V ) |
| 5 | restsspw | ⊢ ( 𝐹 ↾t 𝐴 ) ⊆ 𝒫 𝐴 | |
| 6 | 5 | a1i | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( 𝐹 ↾t 𝐴 ) ⊆ 𝒫 𝐴 ) |
| 7 | fbasne0 | ⊢ ( 𝐹 ∈ ( fBas ‘ 𝑌 ) → 𝐹 ≠ ∅ ) | |
| 8 | 7 | adantr | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → 𝐹 ≠ ∅ ) |
| 9 | n0 | ⊢ ( 𝐹 ≠ ∅ ↔ ∃ 𝑥 𝑥 ∈ 𝐹 ) | |
| 10 | 8 9 | sylib | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ∃ 𝑥 𝑥 ∈ 𝐹 ) |
| 11 | elrestr | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ∈ V ∧ 𝑥 ∈ 𝐹 ) → ( 𝑥 ∩ 𝐴 ) ∈ ( 𝐹 ↾t 𝐴 ) ) | |
| 12 | 11 | 3expia | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ∈ V ) → ( 𝑥 ∈ 𝐹 → ( 𝑥 ∩ 𝐴 ) ∈ ( 𝐹 ↾t 𝐴 ) ) ) |
| 13 | 4 12 | syldan | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( 𝑥 ∈ 𝐹 → ( 𝑥 ∩ 𝐴 ) ∈ ( 𝐹 ↾t 𝐴 ) ) ) |
| 14 | ne0i | ⊢ ( ( 𝑥 ∩ 𝐴 ) ∈ ( 𝐹 ↾t 𝐴 ) → ( 𝐹 ↾t 𝐴 ) ≠ ∅ ) | |
| 15 | 13 14 | syl6 | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( 𝑥 ∈ 𝐹 → ( 𝐹 ↾t 𝐴 ) ≠ ∅ ) ) |
| 16 | 15 | exlimdv | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( ∃ 𝑥 𝑥 ∈ 𝐹 → ( 𝐹 ↾t 𝐴 ) ≠ ∅ ) ) |
| 17 | 10 16 | mpd | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( 𝐹 ↾t 𝐴 ) ≠ ∅ ) |
| 18 | fbasssin | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) → ∃ 𝑥 ∈ 𝐹 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) | |
| 19 | 18 | 3expb | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) → ∃ 𝑥 ∈ 𝐹 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) |
| 20 | 19 | adantlr | ⊢ ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) → ∃ 𝑥 ∈ 𝐹 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) |
| 21 | simplll | ⊢ ( ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) ∧ ( 𝑥 ∈ 𝐹 ∧ 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) ) → 𝐹 ∈ ( fBas ‘ 𝑌 ) ) | |
| 22 | 4 | ad2antrr | ⊢ ( ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) ∧ ( 𝑥 ∈ 𝐹 ∧ 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) ) → 𝐴 ∈ V ) |
| 23 | simprl | ⊢ ( ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) ∧ ( 𝑥 ∈ 𝐹 ∧ 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) ) → 𝑥 ∈ 𝐹 ) | |
| 24 | 21 22 23 11 | syl3anc | ⊢ ( ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) ∧ ( 𝑥 ∈ 𝐹 ∧ 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) ) → ( 𝑥 ∩ 𝐴 ) ∈ ( 𝐹 ↾t 𝐴 ) ) |
| 25 | ssrin | ⊢ ( 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) → ( 𝑥 ∩ 𝐴 ) ⊆ ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) | |
| 26 | 25 | ad2antll | ⊢ ( ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) ∧ ( 𝑥 ∈ 𝐹 ∧ 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) ) → ( 𝑥 ∩ 𝐴 ) ⊆ ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) |
| 27 | vex | ⊢ 𝑥 ∈ V | |
| 28 | 27 | inex1 | ⊢ ( 𝑥 ∩ 𝐴 ) ∈ V |
| 29 | 28 | elpw | ⊢ ( ( 𝑥 ∩ 𝐴 ) ∈ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ↔ ( 𝑥 ∩ 𝐴 ) ⊆ ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) |
| 30 | 26 29 | sylibr | ⊢ ( ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) ∧ ( 𝑥 ∈ 𝐹 ∧ 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) ) → ( 𝑥 ∩ 𝐴 ) ∈ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) |
| 31 | inelcm | ⊢ ( ( ( 𝑥 ∩ 𝐴 ) ∈ ( 𝐹 ↾t 𝐴 ) ∧ ( 𝑥 ∩ 𝐴 ) ∈ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) → ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) ≠ ∅ ) | |
| 32 | 24 30 31 | syl2anc | ⊢ ( ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) ∧ ( 𝑥 ∈ 𝐹 ∧ 𝑥 ⊆ ( 𝑧 ∩ 𝑤 ) ) ) → ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) ≠ ∅ ) |
| 33 | 20 32 | rexlimddv | ⊢ ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ ( 𝑧 ∈ 𝐹 ∧ 𝑤 ∈ 𝐹 ) ) → ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) ≠ ∅ ) |
| 34 | 33 | ralrimivva | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ∀ 𝑧 ∈ 𝐹 ∀ 𝑤 ∈ 𝐹 ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) ≠ ∅ ) |
| 35 | vex | ⊢ 𝑧 ∈ V | |
| 36 | 35 | inex1 | ⊢ ( 𝑧 ∩ 𝐴 ) ∈ V |
| 37 | 36 | a1i | ⊢ ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ 𝑧 ∈ 𝐹 ) → ( 𝑧 ∩ 𝐴 ) ∈ V ) |
| 38 | elrest | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ∈ V ) → ( 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ↔ ∃ 𝑧 ∈ 𝐹 𝑥 = ( 𝑧 ∩ 𝐴 ) ) ) | |
| 39 | 4 38 | syldan | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ↔ ∃ 𝑧 ∈ 𝐹 𝑥 = ( 𝑧 ∩ 𝐴 ) ) ) |
| 40 | vex | ⊢ 𝑤 ∈ V | |
| 41 | 40 | inex1 | ⊢ ( 𝑤 ∩ 𝐴 ) ∈ V |
| 42 | 41 | a1i | ⊢ ( ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ 𝑥 = ( 𝑧 ∩ 𝐴 ) ) ∧ 𝑤 ∈ 𝐹 ) → ( 𝑤 ∩ 𝐴 ) ∈ V ) |
| 43 | elrest | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ∈ V ) → ( 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ↔ ∃ 𝑤 ∈ 𝐹 𝑦 = ( 𝑤 ∩ 𝐴 ) ) ) | |
| 44 | 4 43 | syldan | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ↔ ∃ 𝑤 ∈ 𝐹 𝑦 = ( 𝑤 ∩ 𝐴 ) ) ) |
| 45 | 44 | adantr | ⊢ ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ 𝑥 = ( 𝑧 ∩ 𝐴 ) ) → ( 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ↔ ∃ 𝑤 ∈ 𝐹 𝑦 = ( 𝑤 ∩ 𝐴 ) ) ) |
| 46 | ineq12 | ⊢ ( ( 𝑥 = ( 𝑧 ∩ 𝐴 ) ∧ 𝑦 = ( 𝑤 ∩ 𝐴 ) ) → ( 𝑥 ∩ 𝑦 ) = ( ( 𝑧 ∩ 𝐴 ) ∩ ( 𝑤 ∩ 𝐴 ) ) ) | |
| 47 | inindir | ⊢ ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) = ( ( 𝑧 ∩ 𝐴 ) ∩ ( 𝑤 ∩ 𝐴 ) ) | |
| 48 | 46 47 | eqtr4di | ⊢ ( ( 𝑥 = ( 𝑧 ∩ 𝐴 ) ∧ 𝑦 = ( 𝑤 ∩ 𝐴 ) ) → ( 𝑥 ∩ 𝑦 ) = ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) |
| 49 | 48 | pweqd | ⊢ ( ( 𝑥 = ( 𝑧 ∩ 𝐴 ) ∧ 𝑦 = ( 𝑤 ∩ 𝐴 ) ) → 𝒫 ( 𝑥 ∩ 𝑦 ) = 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) |
| 50 | 49 | ineq2d | ⊢ ( ( 𝑥 = ( 𝑧 ∩ 𝐴 ) ∧ 𝑦 = ( 𝑤 ∩ 𝐴 ) ) → ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) = ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) ) |
| 51 | 50 | neeq1d | ⊢ ( ( 𝑥 = ( 𝑧 ∩ 𝐴 ) ∧ 𝑦 = ( 𝑤 ∩ 𝐴 ) ) → ( ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ↔ ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) ≠ ∅ ) ) |
| 52 | 51 | adantll | ⊢ ( ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ 𝑥 = ( 𝑧 ∩ 𝐴 ) ) ∧ 𝑦 = ( 𝑤 ∩ 𝐴 ) ) → ( ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ↔ ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) ≠ ∅ ) ) |
| 53 | 42 45 52 | ralxfr2d | ⊢ ( ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) ∧ 𝑥 = ( 𝑧 ∩ 𝐴 ) ) → ( ∀ 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ↔ ∀ 𝑤 ∈ 𝐹 ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) ≠ ∅ ) ) |
| 54 | 37 39 53 | ralxfr2d | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( ∀ 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ∀ 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ↔ ∀ 𝑧 ∈ 𝐹 ∀ 𝑤 ∈ 𝐹 ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( ( 𝑧 ∩ 𝑤 ) ∩ 𝐴 ) ) ≠ ∅ ) ) |
| 55 | 34 54 | mpbird | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ∀ 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ∀ 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ) |
| 56 | isfbas | ⊢ ( 𝐴 ∈ V → ( ( 𝐹 ↾t 𝐴 ) ∈ ( fBas ‘ 𝐴 ) ↔ ( ( 𝐹 ↾t 𝐴 ) ⊆ 𝒫 𝐴 ∧ ( ( 𝐹 ↾t 𝐴 ) ≠ ∅ ∧ ∅ ∉ ( 𝐹 ↾t 𝐴 ) ∧ ∀ 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ∀ 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ) ) ) ) | |
| 57 | 56 | baibd | ⊢ ( ( 𝐴 ∈ V ∧ ( 𝐹 ↾t 𝐴 ) ⊆ 𝒫 𝐴 ) → ( ( 𝐹 ↾t 𝐴 ) ∈ ( fBas ‘ 𝐴 ) ↔ ( ( 𝐹 ↾t 𝐴 ) ≠ ∅ ∧ ∅ ∉ ( 𝐹 ↾t 𝐴 ) ∧ ∀ 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ∀ 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ) ) ) |
| 58 | 3anan32 | ⊢ ( ( ( 𝐹 ↾t 𝐴 ) ≠ ∅ ∧ ∅ ∉ ( 𝐹 ↾t 𝐴 ) ∧ ∀ 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ∀ 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ) ↔ ( ( ( 𝐹 ↾t 𝐴 ) ≠ ∅ ∧ ∀ 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ∀ 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ) ∧ ∅ ∉ ( 𝐹 ↾t 𝐴 ) ) ) | |
| 59 | 57 58 | bitrdi | ⊢ ( ( 𝐴 ∈ V ∧ ( 𝐹 ↾t 𝐴 ) ⊆ 𝒫 𝐴 ) → ( ( 𝐹 ↾t 𝐴 ) ∈ ( fBas ‘ 𝐴 ) ↔ ( ( ( 𝐹 ↾t 𝐴 ) ≠ ∅ ∧ ∀ 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ∀ 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ) ∧ ∅ ∉ ( 𝐹 ↾t 𝐴 ) ) ) ) |
| 60 | 59 | baibd | ⊢ ( ( ( 𝐴 ∈ V ∧ ( 𝐹 ↾t 𝐴 ) ⊆ 𝒫 𝐴 ) ∧ ( ( 𝐹 ↾t 𝐴 ) ≠ ∅ ∧ ∀ 𝑥 ∈ ( 𝐹 ↾t 𝐴 ) ∀ 𝑦 ∈ ( 𝐹 ↾t 𝐴 ) ( ( 𝐹 ↾t 𝐴 ) ∩ 𝒫 ( 𝑥 ∩ 𝑦 ) ) ≠ ∅ ) ) → ( ( 𝐹 ↾t 𝐴 ) ∈ ( fBas ‘ 𝐴 ) ↔ ∅ ∉ ( 𝐹 ↾t 𝐴 ) ) ) |
| 61 | 4 6 17 55 60 | syl22anc | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( ( 𝐹 ↾t 𝐴 ) ∈ ( fBas ‘ 𝐴 ) ↔ ∅ ∉ ( 𝐹 ↾t 𝐴 ) ) ) |
| 62 | df-nel | ⊢ ( ∅ ∉ ( 𝐹 ↾t 𝐴 ) ↔ ¬ ∅ ∈ ( 𝐹 ↾t 𝐴 ) ) | |
| 63 | 61 62 | bitrdi | ⊢ ( ( 𝐹 ∈ ( fBas ‘ 𝑌 ) ∧ 𝐴 ⊆ 𝑌 ) → ( ( 𝐹 ↾t 𝐴 ) ∈ ( fBas ‘ 𝐴 ) ↔ ¬ ∅ ∈ ( 𝐹 ↾t 𝐴 ) ) ) |