Proof of Theorem relrelss
| Step | Hyp | Ref
 | Expression | 
| 1 |   | df-rel 4670 | 
. . 3
⊢ (Rel dom
𝐴 ↔ dom 𝐴 ⊆ (V ×
V)) | 
| 2 | 1 | anbi2i 457 | 
. 2
⊢ ((Rel
𝐴 ∧ Rel dom 𝐴) ↔ (Rel 𝐴 ∧ dom 𝐴 ⊆ (V × V))) | 
| 3 |   | relssdmrn 5190 | 
. . . 4
⊢ (Rel
𝐴 → 𝐴 ⊆ (dom 𝐴 × ran 𝐴)) | 
| 4 |   | ssv 3205 | 
. . . . 5
⊢ ran 𝐴 ⊆ V | 
| 5 |   | xpss12 4770 | 
. . . . 5
⊢ ((dom
𝐴 ⊆ (V × V)
∧ ran 𝐴 ⊆ V)
→ (dom 𝐴 × ran
𝐴) ⊆ ((V × V)
× V)) | 
| 6 | 4, 5 | mpan2 425 | 
. . . 4
⊢ (dom
𝐴 ⊆ (V × V)
→ (dom 𝐴 × ran
𝐴) ⊆ ((V × V)
× V)) | 
| 7 | 3, 6 | sylan9ss 3196 | 
. . 3
⊢ ((Rel
𝐴 ∧ dom 𝐴 ⊆ (V × V)) →
𝐴 ⊆ ((V × V)
× V)) | 
| 8 |   | xpss 4771 | 
. . . . . 6
⊢ ((V
× V) × V) ⊆ (V × V) | 
| 9 |   | sstr 3191 | 
. . . . . 6
⊢ ((𝐴 ⊆ ((V × V) ×
V) ∧ ((V × V) × V) ⊆ (V × V)) → 𝐴 ⊆ (V ×
V)) | 
| 10 | 8, 9 | mpan2 425 | 
. . . . 5
⊢ (𝐴 ⊆ ((V × V) ×
V) → 𝐴 ⊆ (V
× V)) | 
| 11 |   | df-rel 4670 | 
. . . . 5
⊢ (Rel
𝐴 ↔ 𝐴 ⊆ (V × V)) | 
| 12 | 10, 11 | sylibr 134 | 
. . . 4
⊢ (𝐴 ⊆ ((V × V) ×
V) → Rel 𝐴) | 
| 13 |   | dmss 4865 | 
. . . . 5
⊢ (𝐴 ⊆ ((V × V) ×
V) → dom 𝐴 ⊆ dom
((V × V) × V)) | 
| 14 |   | vn0m 3462 | 
. . . . . 6
⊢
∃𝑥 𝑥 ∈ V | 
| 15 |   | dmxpm 4886 | 
. . . . . 6
⊢
(∃𝑥 𝑥 ∈ V → dom ((V ×
V) × V) = (V × V)) | 
| 16 | 14, 15 | ax-mp 5 | 
. . . . 5
⊢ dom ((V
× V) × V) = (V × V) | 
| 17 | 13, 16 | sseqtrdi 3231 | 
. . . 4
⊢ (𝐴 ⊆ ((V × V) ×
V) → dom 𝐴 ⊆ (V
× V)) | 
| 18 | 12, 17 | jca 306 | 
. . 3
⊢ (𝐴 ⊆ ((V × V) ×
V) → (Rel 𝐴 ∧ dom
𝐴 ⊆ (V ×
V))) | 
| 19 | 7, 18 | impbii 126 | 
. 2
⊢ ((Rel
𝐴 ∧ dom 𝐴 ⊆ (V × V)) ↔
𝐴 ⊆ ((V × V)
× V)) | 
| 20 | 2, 19 | bitri 184 | 
1
⊢ ((Rel
𝐴 ∧ Rel dom 𝐴) ↔ 𝐴 ⊆ ((V × V) ×
V)) |