| Step | Hyp | Ref
 | Expression | 
| 1 |   | funtopon 14248 | 
. . . . 5
⊢ Fun
TopOn | 
| 2 |   | funrel 5275 | 
. . . . 5
⊢ (Fun
TopOn → Rel TopOn) | 
| 3 | 1, 2 | ax-mp 5 | 
. . . 4
⊢ Rel
TopOn | 
| 4 |   | relelfvdm 5590 | 
. . . 4
⊢ ((Rel
TopOn ∧ 𝐽 ∈
(TopOn‘𝐵)) →
𝐵 ∈ dom
TopOn) | 
| 5 | 3, 4 | mpan 424 | 
. . 3
⊢ (𝐽 ∈ (TopOn‘𝐵) → 𝐵 ∈ dom TopOn) | 
| 6 | 5 | elexd 2776 | 
. 2
⊢ (𝐽 ∈ (TopOn‘𝐵) → 𝐵 ∈ V) | 
| 7 |   | uniexg 4474 | 
. . . 4
⊢ (𝐽 ∈ Top → ∪ 𝐽
∈ V) | 
| 8 |   | eleq1 2259 | 
. . . 4
⊢ (𝐵 = ∪
𝐽 → (𝐵 ∈ V ↔ ∪ 𝐽
∈ V)) | 
| 9 | 7, 8 | syl5ibrcom 157 | 
. . 3
⊢ (𝐽 ∈ Top → (𝐵 = ∪
𝐽 → 𝐵 ∈ V)) | 
| 10 | 9 | imp 124 | 
. 2
⊢ ((𝐽 ∈ Top ∧ 𝐵 = ∪
𝐽) → 𝐵 ∈ V) | 
| 11 |   | eqeq1 2203 | 
. . . . . 6
⊢ (𝑏 = 𝐵 → (𝑏 = ∪ 𝑗 ↔ 𝐵 = ∪ 𝑗)) | 
| 12 | 11 | rabbidv 2752 | 
. . . . 5
⊢ (𝑏 = 𝐵 → {𝑗 ∈ Top ∣ 𝑏 = ∪ 𝑗} = {𝑗 ∈ Top ∣ 𝐵 = ∪ 𝑗}) | 
| 13 |   | df-topon 14247 | 
. . . . 5
⊢ TopOn =
(𝑏 ∈ V ↦ {𝑗 ∈ Top ∣ 𝑏 = ∪
𝑗}) | 
| 14 |   | vpwex 4212 | 
. . . . . . 7
⊢ 𝒫
𝑏 ∈ V | 
| 15 | 14 | pwex 4216 | 
. . . . . 6
⊢ 𝒫
𝒫 𝑏 ∈
V | 
| 16 |   | rabss 3260 | 
. . . . . . 7
⊢ ({𝑗 ∈ Top ∣ 𝑏 = ∪
𝑗} ⊆ 𝒫
𝒫 𝑏 ↔
∀𝑗 ∈ Top (𝑏 = ∪
𝑗 → 𝑗 ∈ 𝒫 𝒫 𝑏)) | 
| 17 |   | pwuni 4225 | 
. . . . . . . . . 10
⊢ 𝑗 ⊆ 𝒫 ∪ 𝑗 | 
| 18 |   | pweq 3608 | 
. . . . . . . . . 10
⊢ (𝑏 = ∪
𝑗 → 𝒫 𝑏 = 𝒫 ∪ 𝑗) | 
| 19 | 17, 18 | sseqtrrid 3234 | 
. . . . . . . . 9
⊢ (𝑏 = ∪
𝑗 → 𝑗 ⊆ 𝒫 𝑏) | 
| 20 |   | velpw 3612 | 
. . . . . . . . 9
⊢ (𝑗 ∈ 𝒫 𝒫
𝑏 ↔ 𝑗 ⊆ 𝒫 𝑏) | 
| 21 | 19, 20 | sylibr 134 | 
. . . . . . . 8
⊢ (𝑏 = ∪
𝑗 → 𝑗 ∈ 𝒫 𝒫 𝑏) | 
| 22 | 21 | a1i 9 | 
. . . . . . 7
⊢ (𝑗 ∈ Top → (𝑏 = ∪
𝑗 → 𝑗 ∈ 𝒫 𝒫 𝑏)) | 
| 23 | 16, 22 | mprgbir 2555 | 
. . . . . 6
⊢ {𝑗 ∈ Top ∣ 𝑏 = ∪
𝑗} ⊆ 𝒫
𝒫 𝑏 | 
| 24 | 15, 23 | ssexi 4171 | 
. . . . 5
⊢ {𝑗 ∈ Top ∣ 𝑏 = ∪
𝑗} ∈
V | 
| 25 | 12, 13, 24 | fvmpt3i 5641 | 
. . . 4
⊢ (𝐵 ∈ V →
(TopOn‘𝐵) = {𝑗 ∈ Top ∣ 𝐵 = ∪
𝑗}) | 
| 26 | 25 | eleq2d 2266 | 
. . 3
⊢ (𝐵 ∈ V → (𝐽 ∈ (TopOn‘𝐵) ↔ 𝐽 ∈ {𝑗 ∈ Top ∣ 𝐵 = ∪ 𝑗})) | 
| 27 |   | unieq 3848 | 
. . . . 5
⊢ (𝑗 = 𝐽 → ∪ 𝑗 = ∪
𝐽) | 
| 28 | 27 | eqeq2d 2208 | 
. . . 4
⊢ (𝑗 = 𝐽 → (𝐵 = ∪ 𝑗 ↔ 𝐵 = ∪ 𝐽)) | 
| 29 | 28 | elrab 2920 | 
. . 3
⊢ (𝐽 ∈ {𝑗 ∈ Top ∣ 𝐵 = ∪ 𝑗} ↔ (𝐽 ∈ Top ∧ 𝐵 = ∪ 𝐽)) | 
| 30 | 26, 29 | bitrdi 196 | 
. 2
⊢ (𝐵 ∈ V → (𝐽 ∈ (TopOn‘𝐵) ↔ (𝐽 ∈ Top ∧ 𝐵 = ∪ 𝐽))) | 
| 31 | 6, 10, 30 | pm5.21nii 705 | 
1
⊢ (𝐽 ∈ (TopOn‘𝐵) ↔ (𝐽 ∈ Top ∧ 𝐵 = ∪ 𝐽)) |