| Step | Hyp | Ref
 | Expression | 
| 1 |   | simpl 109 | 
. . . . . . 7
⊢
((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) → ∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦)) | 
| 2 |   | nninfex 7187 | 
. . . . . . . . . 10
⊢
ℕ∞ ∈ V | 
| 3 |   | fconstmpt 4710 | 
. . . . . . . . . . . . . . 15
⊢ (ω
× {∅}) = (𝑖
∈ ω ↦ ∅) | 
| 4 |   | 0nninf 15648 | 
. . . . . . . . . . . . . . 15
⊢ (ω
× {∅}) ∈ ℕ∞ | 
| 5 | 3, 4 | eqeltrri 2270 | 
. . . . . . . . . . . . . 14
⊢ (𝑖 ∈ ω ↦ ∅)
∈ ℕ∞ | 
| 6 | 5 | fconst6 5457 | 
. . . . . . . . . . . . 13
⊢ (𝑧 × {(𝑖 ∈ ω ↦ ∅)}):𝑧⟶ℕ∞ | 
| 7 | 6 | a1i 9 | 
. . . . . . . . . . . 12
⊢ (𝑧 ⊆ {∅} → (𝑧 × {(𝑖 ∈ ω ↦ ∅)}):𝑧⟶ℕ∞) | 
| 8 |   | ssel 3177 | 
. . . . . . . . . . . . . . . . . 18
⊢ (𝑧 ⊆ {∅} → (𝑢 ∈ 𝑧 → 𝑢 ∈ {∅})) | 
| 9 |   | elsni 3640 | 
. . . . . . . . . . . . . . . . . 18
⊢ (𝑢 ∈ {∅} → 𝑢 = ∅) | 
| 10 | 8, 9 | syl6 33 | 
. . . . . . . . . . . . . . . . 17
⊢ (𝑧 ⊆ {∅} → (𝑢 ∈ 𝑧 → 𝑢 = ∅)) | 
| 11 |   | ssel 3177 | 
. . . . . . . . . . . . . . . . . 18
⊢ (𝑧 ⊆ {∅} → (𝑣 ∈ 𝑧 → 𝑣 ∈ {∅})) | 
| 12 |   | elsni 3640 | 
. . . . . . . . . . . . . . . . . 18
⊢ (𝑣 ∈ {∅} → 𝑣 = ∅) | 
| 13 | 11, 12 | syl6 33 | 
. . . . . . . . . . . . . . . . 17
⊢ (𝑧 ⊆ {∅} → (𝑣 ∈ 𝑧 → 𝑣 = ∅)) | 
| 14 | 10, 13 | anim12d 335 | 
. . . . . . . . . . . . . . . 16
⊢ (𝑧 ⊆ {∅} →
((𝑢 ∈ 𝑧 ∧ 𝑣 ∈ 𝑧) → (𝑢 = ∅ ∧ 𝑣 = ∅))) | 
| 15 |   | eqtr3 2216 | 
. . . . . . . . . . . . . . . 16
⊢ ((𝑢 = ∅ ∧ 𝑣 = ∅) → 𝑢 = 𝑣) | 
| 16 | 14, 15 | syl6 33 | 
. . . . . . . . . . . . . . 15
⊢ (𝑧 ⊆ {∅} →
((𝑢 ∈ 𝑧 ∧ 𝑣 ∈ 𝑧) → 𝑢 = 𝑣)) | 
| 17 | 16 | imp 124 | 
. . . . . . . . . . . . . 14
⊢ ((𝑧 ⊆ {∅} ∧ (𝑢 ∈ 𝑧 ∧ 𝑣 ∈ 𝑧)) → 𝑢 = 𝑣) | 
| 18 | 17 | a1d 22 | 
. . . . . . . . . . . . 13
⊢ ((𝑧 ⊆ {∅} ∧ (𝑢 ∈ 𝑧 ∧ 𝑣 ∈ 𝑧)) → (((𝑧 × {(𝑖 ∈ ω ↦
∅)})‘𝑢) =
((𝑧 × {(𝑖 ∈ ω ↦
∅)})‘𝑣) →
𝑢 = 𝑣)) | 
| 19 | 18 | ralrimivva 2579 | 
. . . . . . . . . . . 12
⊢ (𝑧 ⊆ {∅} →
∀𝑢 ∈ 𝑧 ∀𝑣 ∈ 𝑧 (((𝑧 × {(𝑖 ∈ ω ↦
∅)})‘𝑢) =
((𝑧 × {(𝑖 ∈ ω ↦
∅)})‘𝑣) →
𝑢 = 𝑣)) | 
| 20 |   | dff13 5815 | 
. . . . . . . . . . . 12
⊢ ((𝑧 × {(𝑖 ∈ ω ↦ ∅)}):𝑧–1-1→ℕ∞ ↔ ((𝑧 × {(𝑖 ∈ ω ↦ ∅)}):𝑧⟶ℕ∞ ∧
∀𝑢 ∈ 𝑧 ∀𝑣 ∈ 𝑧 (((𝑧 × {(𝑖 ∈ ω ↦
∅)})‘𝑢) =
((𝑧 × {(𝑖 ∈ ω ↦
∅)})‘𝑣) →
𝑢 = 𝑣))) | 
| 21 | 7, 19, 20 | sylanbrc 417 | 
. . . . . . . . . . 11
⊢ (𝑧 ⊆ {∅} → (𝑧 × {(𝑖 ∈ ω ↦ ∅)}):𝑧–1-1→ℕ∞) | 
| 22 |   | exmidsbthrlem.s | 
. . . . . . . . . . . . 13
⊢ 𝑆 = (𝑝 ∈ ℕ∞ ↦
(𝑖 ∈ ω ↦
if(𝑖 = ∅,
1o, (𝑝‘∪ 𝑖)))) | 
| 23 | 22 | peano4nninf 15650 | 
. . . . . . . . . . . 12
⊢ 𝑆:ℕ∞–1-1→ℕ∞ | 
| 24 | 23 | a1i 9 | 
. . . . . . . . . . 11
⊢ (𝑧 ⊆ {∅} → 𝑆:ℕ∞–1-1→ℕ∞) | 
| 25 |   | disj 3499 | 
. . . . . . . . . . . . 13
⊢ ((ran
(𝑧 × {(𝑖 ∈ ω ↦
∅)}) ∩ ran 𝑆) =
∅ ↔ ∀𝑎
∈ ran (𝑧 ×
{(𝑖 ∈ ω ↦
∅)}) ¬ 𝑎 ∈
ran 𝑆) | 
| 26 | 22 | peano3nninf 15651 | 
. . . . . . . . . . . . . . . . . . 19
⊢ (𝑏 ∈
ℕ∞ → (𝑆‘𝑏) ≠ (𝑘 ∈ ω ↦
∅)) | 
| 27 |   | eqidd 2197 | 
. . . . . . . . . . . . . . . . . . . . 21
⊢ (𝑘 = 𝑖 → ∅ = ∅) | 
| 28 | 27 | cbvmptv 4129 | 
. . . . . . . . . . . . . . . . . . . 20
⊢ (𝑘 ∈ ω ↦ ∅)
= (𝑖 ∈ ω ↦
∅) | 
| 29 | 28 | neeq2i 2383 | 
. . . . . . . . . . . . . . . . . . 19
⊢ ((𝑆‘𝑏) ≠ (𝑘 ∈ ω ↦ ∅) ↔
(𝑆‘𝑏) ≠ (𝑖 ∈ ω ↦
∅)) | 
| 30 | 26, 29 | sylib 122 | 
. . . . . . . . . . . . . . . . . 18
⊢ (𝑏 ∈
ℕ∞ → (𝑆‘𝑏) ≠ (𝑖 ∈ ω ↦
∅)) | 
| 31 | 30 | neneqd 2388 | 
. . . . . . . . . . . . . . . . 17
⊢ (𝑏 ∈
ℕ∞ → ¬ (𝑆‘𝑏) = (𝑖 ∈ ω ↦
∅)) | 
| 32 | 31 | nrex 2589 | 
. . . . . . . . . . . . . . . 16
⊢  ¬
∃𝑏 ∈
ℕ∞ (𝑆‘𝑏) = (𝑖 ∈ ω ↦
∅) | 
| 33 |   | f1dm 5468 | 
. . . . . . . . . . . . . . . . . 18
⊢ (𝑆:ℕ∞–1-1→ℕ∞ → dom
𝑆 =
ℕ∞) | 
| 34 | 23, 33 | ax-mp 5 | 
. . . . . . . . . . . . . . . . 17
⊢ dom 𝑆 =
ℕ∞ | 
| 35 |   | eqcom 2198 | 
. . . . . . . . . . . . . . . . 17
⊢ ((𝑖 ∈ ω ↦ ∅)
= (𝑆‘𝑏) ↔ (𝑆‘𝑏) = (𝑖 ∈ ω ↦
∅)) | 
| 36 | 34, 35 | rexeqbii 2510 | 
. . . . . . . . . . . . . . . 16
⊢
(∃𝑏 ∈ dom
𝑆(𝑖 ∈ ω ↦ ∅) = (𝑆‘𝑏) ↔ ∃𝑏 ∈ ℕ∞ (𝑆‘𝑏) = (𝑖 ∈ ω ↦
∅)) | 
| 37 | 32, 36 | mtbir 672 | 
. . . . . . . . . . . . . . 15
⊢  ¬
∃𝑏 ∈ dom 𝑆(𝑖 ∈ ω ↦ ∅) = (𝑆‘𝑏) | 
| 38 | 22 | funmpt2 5297 | 
. . . . . . . . . . . . . . . 16
⊢ Fun 𝑆 | 
| 39 |   | elrnrexdm 5701 | 
. . . . . . . . . . . . . . . 16
⊢ (Fun
𝑆 → ((𝑖 ∈ ω ↦ ∅)
∈ ran 𝑆 →
∃𝑏 ∈ dom 𝑆(𝑖 ∈ ω ↦ ∅) = (𝑆‘𝑏))) | 
| 40 | 38, 39 | ax-mp 5 | 
. . . . . . . . . . . . . . 15
⊢ ((𝑖 ∈ ω ↦ ∅)
∈ ran 𝑆 →
∃𝑏 ∈ dom 𝑆(𝑖 ∈ ω ↦ ∅) = (𝑆‘𝑏)) | 
| 41 | 37, 40 | mto 663 | 
. . . . . . . . . . . . . 14
⊢  ¬
(𝑖 ∈ ω ↦
∅) ∈ ran 𝑆 | 
| 42 |   | rnxpss 5101 | 
. . . . . . . . . . . . . . . . 17
⊢ ran
(𝑧 × {(𝑖 ∈ ω ↦
∅)}) ⊆ {(𝑖
∈ ω ↦ ∅)} | 
| 43 | 42 | sseli 3179 | 
. . . . . . . . . . . . . . . 16
⊢ (𝑎 ∈ ran (𝑧 × {(𝑖 ∈ ω ↦ ∅)}) →
𝑎 ∈ {(𝑖 ∈ ω ↦
∅)}) | 
| 44 |   | elsni 3640 | 
. . . . . . . . . . . . . . . 16
⊢ (𝑎 ∈ {(𝑖 ∈ ω ↦ ∅)} →
𝑎 = (𝑖 ∈ ω ↦
∅)) | 
| 45 | 43, 44 | syl 14 | 
. . . . . . . . . . . . . . 15
⊢ (𝑎 ∈ ran (𝑧 × {(𝑖 ∈ ω ↦ ∅)}) →
𝑎 = (𝑖 ∈ ω ↦
∅)) | 
| 46 | 45 | eleq1d 2265 | 
. . . . . . . . . . . . . 14
⊢ (𝑎 ∈ ran (𝑧 × {(𝑖 ∈ ω ↦ ∅)}) →
(𝑎 ∈ ran 𝑆 ↔ (𝑖 ∈ ω ↦ ∅) ∈ ran
𝑆)) | 
| 47 | 41, 46 | mtbiri 676 | 
. . . . . . . . . . . . 13
⊢ (𝑎 ∈ ran (𝑧 × {(𝑖 ∈ ω ↦ ∅)}) →
¬ 𝑎 ∈ ran 𝑆) | 
| 48 | 25, 47 | mprgbir 2555 | 
. . . . . . . . . . . 12
⊢ (ran
(𝑧 × {(𝑖 ∈ ω ↦
∅)}) ∩ ran 𝑆) =
∅ | 
| 49 | 48 | a1i 9 | 
. . . . . . . . . . 11
⊢ (𝑧 ⊆ {∅} → (ran
(𝑧 × {(𝑖 ∈ ω ↦
∅)}) ∩ ran 𝑆) =
∅) | 
| 50 | 21, 24, 49 | casef1 7156 | 
. . . . . . . . . 10
⊢ (𝑧 ⊆ {∅} →
case((𝑧 × {(𝑖 ∈ ω ↦
∅)}), 𝑆):(𝑧 ⊔
ℕ∞)–1-1→ℕ∞) | 
| 51 |   | f1domg 6817 | 
. . . . . . . . . 10
⊢
(ℕ∞ ∈ V → (case((𝑧 × {(𝑖 ∈ ω ↦ ∅)}), 𝑆):(𝑧 ⊔
ℕ∞)–1-1→ℕ∞ → (𝑧 ⊔
ℕ∞) ≼
ℕ∞)) | 
| 52 | 2, 50, 51 | mpsyl 65 | 
. . . . . . . . 9
⊢ (𝑧 ⊆ {∅} → (𝑧 ⊔
ℕ∞) ≼
ℕ∞) | 
| 53 | 52 | adantl 277 | 
. . . . . . . 8
⊢
((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) → (𝑧 ⊔
ℕ∞) ≼
ℕ∞) | 
| 54 |   | inrresf1 7128 | 
. . . . . . . . 9
⊢ (inr
↾ ℕ∞):ℕ∞–1-1→(𝑧 ⊔
ℕ∞) | 
| 55 |   | vex 2766 | 
. . . . . . . . . . 11
⊢ 𝑧 ∈ V | 
| 56 |   | djuex 7109 | 
. . . . . . . . . . 11
⊢ ((𝑧 ∈ V ∧
ℕ∞ ∈ V) → (𝑧 ⊔ ℕ∞) ∈
V) | 
| 57 | 55, 2, 56 | mp2an 426 | 
. . . . . . . . . 10
⊢ (𝑧 ⊔
ℕ∞) ∈ V | 
| 58 | 57 | f1dom 6819 | 
. . . . . . . . 9
⊢ ((inr
↾ ℕ∞):ℕ∞–1-1→(𝑧 ⊔ ℕ∞) →
ℕ∞ ≼ (𝑧 ⊔
ℕ∞)) | 
| 59 | 54, 58 | ax-mp 5 | 
. . . . . . . 8
⊢
ℕ∞ ≼ (𝑧 ⊔
ℕ∞) | 
| 60 | 53, 59 | jctir 313 | 
. . . . . . 7
⊢
((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) → ((𝑧 ⊔
ℕ∞) ≼ ℕ∞ ∧
ℕ∞ ≼ (𝑧 ⊔
ℕ∞))) | 
| 61 |   | breq12 4038 | 
. . . . . . . . . . 11
⊢ ((𝑥 = (𝑧 ⊔ ℕ∞) ∧
𝑦 =
ℕ∞) → (𝑥 ≼ 𝑦 ↔ (𝑧 ⊔ ℕ∞) ≼
ℕ∞)) | 
| 62 |   | breq12 4038 | 
. . . . . . . . . . . 12
⊢ ((𝑦 = ℕ∞
∧ 𝑥 = (𝑧 ⊔
ℕ∞)) → (𝑦 ≼ 𝑥 ↔ ℕ∞ ≼
(𝑧 ⊔
ℕ∞))) | 
| 63 | 62 | ancoms 268 | 
. . . . . . . . . . 11
⊢ ((𝑥 = (𝑧 ⊔ ℕ∞) ∧
𝑦 =
ℕ∞) → (𝑦 ≼ 𝑥 ↔ ℕ∞ ≼
(𝑧 ⊔
ℕ∞))) | 
| 64 | 61, 63 | anbi12d 473 | 
. . . . . . . . . 10
⊢ ((𝑥 = (𝑧 ⊔ ℕ∞) ∧
𝑦 =
ℕ∞) → ((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) ↔ ((𝑧 ⊔ ℕ∞) ≼
ℕ∞ ∧ ℕ∞ ≼ (𝑧 ⊔
ℕ∞)))) | 
| 65 |   | breq12 4038 | 
. . . . . . . . . 10
⊢ ((𝑥 = (𝑧 ⊔ ℕ∞) ∧
𝑦 =
ℕ∞) → (𝑥 ≈ 𝑦 ↔ (𝑧 ⊔ ℕ∞) ≈
ℕ∞)) | 
| 66 | 64, 65 | imbi12d 234 | 
. . . . . . . . 9
⊢ ((𝑥 = (𝑧 ⊔ ℕ∞) ∧
𝑦 =
ℕ∞) → (((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ↔ (((𝑧 ⊔ ℕ∞) ≼
ℕ∞ ∧ ℕ∞ ≼ (𝑧 ⊔
ℕ∞)) → (𝑧 ⊔ ℕ∞) ≈
ℕ∞))) | 
| 67 | 66 | spc2gv 2855 | 
. . . . . . . 8
⊢ (((𝑧 ⊔
ℕ∞) ∈ V ∧ ℕ∞ ∈ V)
→ (∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) → (((𝑧 ⊔ ℕ∞) ≼
ℕ∞ ∧ ℕ∞ ≼ (𝑧 ⊔
ℕ∞)) → (𝑧 ⊔ ℕ∞) ≈
ℕ∞))) | 
| 68 | 57, 2, 67 | mp2an 426 | 
. . . . . . 7
⊢
(∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) → (((𝑧 ⊔ ℕ∞) ≼
ℕ∞ ∧ ℕ∞ ≼ (𝑧 ⊔
ℕ∞)) → (𝑧 ⊔ ℕ∞) ≈
ℕ∞)) | 
| 69 | 1, 60, 68 | sylc 62 | 
. . . . . 6
⊢
((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) → (𝑧 ⊔
ℕ∞) ≈
ℕ∞) | 
| 70 |   | bren 6806 | 
. . . . . 6
⊢ ((𝑧 ⊔
ℕ∞) ≈ ℕ∞ ↔
∃𝑓 𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞) | 
| 71 | 69, 70 | sylib 122 | 
. . . . 5
⊢
((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) → ∃𝑓 𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞) | 
| 72 |   | nninfomni 15663 | 
. . . . . . . . 9
⊢
ℕ∞ ∈ Omni | 
| 73 | 72 | a1i 9 | 
. . . . . . . 8
⊢
(((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) ∧ 𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞) →
ℕ∞ ∈ Omni) | 
| 74 |   | f1ocnv 5517 | 
. . . . . . . . . 10
⊢ (𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞ → ◡𝑓:ℕ∞–1-1-onto→(𝑧 ⊔
ℕ∞)) | 
| 75 |   | f1ofo 5511 | 
. . . . . . . . . 10
⊢ (◡𝑓:ℕ∞–1-1-onto→(𝑧 ⊔ ℕ∞) →
◡𝑓:ℕ∞–onto→(𝑧 ⊔
ℕ∞)) | 
| 76 | 74, 75 | syl 14 | 
. . . . . . . . 9
⊢ (𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞ → ◡𝑓:ℕ∞–onto→(𝑧 ⊔
ℕ∞)) | 
| 77 | 76 | adantl 277 | 
. . . . . . . 8
⊢
(((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) ∧ 𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞) → ◡𝑓:ℕ∞–onto→(𝑧 ⊔
ℕ∞)) | 
| 78 | 73, 77 | fodjuomni 7215 | 
. . . . . . 7
⊢
(((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) ∧ 𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞) →
(∃𝑤 𝑤 ∈ 𝑧 ∨ 𝑧 = ∅)) | 
| 79 |   | sssnm 3784 | 
. . . . . . . . . 10
⊢
(∃𝑤 𝑤 ∈ 𝑧 → (𝑧 ⊆ {∅} ↔ 𝑧 = {∅})) | 
| 80 | 79 | biimpcd 159 | 
. . . . . . . . 9
⊢ (𝑧 ⊆ {∅} →
(∃𝑤 𝑤 ∈ 𝑧 → 𝑧 = {∅})) | 
| 81 | 80 | ad2antlr 489 | 
. . . . . . . 8
⊢
(((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) ∧ 𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞) →
(∃𝑤 𝑤 ∈ 𝑧 → 𝑧 = {∅})) | 
| 82 | 81 | orim1d 788 | 
. . . . . . 7
⊢
(((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) ∧ 𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞) →
((∃𝑤 𝑤 ∈ 𝑧 ∨ 𝑧 = ∅) → (𝑧 = {∅} ∨ 𝑧 = ∅))) | 
| 83 | 78, 82 | mpd 13 | 
. . . . . 6
⊢
(((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) ∧ 𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞) → (𝑧 = {∅} ∨ 𝑧 = ∅)) | 
| 84 | 83 | orcomd 730 | 
. . . . 5
⊢
(((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) ∧ 𝑓:(𝑧 ⊔
ℕ∞)–1-1-onto→ℕ∞) → (𝑧 = ∅ ∨ 𝑧 = {∅})) | 
| 85 | 71, 84 | exlimddv 1913 | 
. . . 4
⊢
((∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) ∧ 𝑧 ⊆ {∅}) → (𝑧 = ∅ ∨ 𝑧 = {∅})) | 
| 86 | 85 | ex 115 | 
. . 3
⊢
(∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) → (𝑧 ⊆ {∅} → (𝑧 = ∅ ∨ 𝑧 = {∅}))) | 
| 87 | 86 | alrimiv 1888 | 
. 2
⊢
(∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) → ∀𝑧(𝑧 ⊆ {∅} → (𝑧 = ∅ ∨ 𝑧 = {∅}))) | 
| 88 |   | exmid01 4231 | 
. 2
⊢
(EXMID ↔ ∀𝑧(𝑧 ⊆ {∅} → (𝑧 = ∅ ∨ 𝑧 = {∅}))) | 
| 89 | 87, 88 | sylibr 134 | 
1
⊢
(∀𝑥∀𝑦((𝑥 ≼ 𝑦 ∧ 𝑦 ≼ 𝑥) → 𝑥 ≈ 𝑦) →
EXMID) |