| Step | Hyp | Ref
 | Expression | 
| 1 |   | simpl 109 | 
. . . 4
⊢
((CHOICE ∧ 𝑦 ⊆ {∅}) →
CHOICE) | 
| 2 |   | exmidaclem.c | 
. . . . . 6
⊢ 𝐶 = {𝐴, 𝐵} | 
| 3 |   | exmidaclem.a | 
. . . . . . . 8
⊢ 𝐴 = {𝑥 ∈ {∅, {∅}} ∣ (𝑥 = ∅ ∨ 𝑦 = {∅})} | 
| 4 |   | pp0ex 4222 | 
. . . . . . . . 9
⊢ {∅,
{∅}} ∈ V | 
| 5 | 4 | rabex 4177 | 
. . . . . . . 8
⊢ {𝑥 ∈ {∅, {∅}}
∣ (𝑥 = ∅ ∨
𝑦 = {∅})} ∈
V | 
| 6 | 3, 5 | eqeltri 2269 | 
. . . . . . 7
⊢ 𝐴 ∈ V | 
| 7 |   | exmidaclem.b | 
. . . . . . . 8
⊢ 𝐵 = {𝑥 ∈ {∅, {∅}} ∣ (𝑥 = {∅} ∨ 𝑦 = {∅})} | 
| 8 | 4 | rabex 4177 | 
. . . . . . . 8
⊢ {𝑥 ∈ {∅, {∅}}
∣ (𝑥 = {∅} ∨
𝑦 = {∅})} ∈
V | 
| 9 | 7, 8 | eqeltri 2269 | 
. . . . . . 7
⊢ 𝐵 ∈ V | 
| 10 |   | prexg 4244 | 
. . . . . . 7
⊢ ((𝐴 ∈ V ∧ 𝐵 ∈ V) → {𝐴, 𝐵} ∈ V) | 
| 11 | 6, 9, 10 | mp2an 426 | 
. . . . . 6
⊢ {𝐴, 𝐵} ∈ V | 
| 12 | 2, 11 | eqeltri 2269 | 
. . . . 5
⊢ 𝐶 ∈ V | 
| 13 | 12 | a1i 9 | 
. . . 4
⊢
((CHOICE ∧ 𝑦 ⊆ {∅}) → 𝐶 ∈ V) | 
| 14 |   | simpr 110 | 
. . . . . . 7
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ 𝑧 ∈ 𝐶) → 𝑧 ∈ 𝐶) | 
| 15 | 14, 2 | eleqtrdi 2289 | 
. . . . . 6
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ 𝑧 ∈ 𝐶) → 𝑧 ∈ {𝐴, 𝐵}) | 
| 16 |   | elpri 3645 | 
. . . . . 6
⊢ (𝑧 ∈ {𝐴, 𝐵} → (𝑧 = 𝐴 ∨ 𝑧 = 𝐵)) | 
| 17 |   | 0ex 4160 | 
. . . . . . . . . . 11
⊢ ∅
∈ V | 
| 18 | 17 | prid1 3728 | 
. . . . . . . . . 10
⊢ ∅
∈ {∅, {∅}} | 
| 19 |   | eqid 2196 | 
. . . . . . . . . . 11
⊢ ∅ =
∅ | 
| 20 | 19 | orci 732 | 
. . . . . . . . . 10
⊢ (∅
= ∅ ∨ 𝑦 =
{∅}) | 
| 21 |   | eqeq1 2203 | 
. . . . . . . . . . . 12
⊢ (𝑥 = ∅ → (𝑥 = ∅ ↔ ∅ =
∅)) | 
| 22 | 21 | orbi1d 792 | 
. . . . . . . . . . 11
⊢ (𝑥 = ∅ → ((𝑥 = ∅ ∨ 𝑦 = {∅}) ↔ (∅ =
∅ ∨ 𝑦 =
{∅}))) | 
| 23 | 22, 3 | elrab2 2923 | 
. . . . . . . . . 10
⊢ (∅
∈ 𝐴 ↔ (∅
∈ {∅, {∅}} ∧ (∅ = ∅ ∨ 𝑦 = {∅}))) | 
| 24 | 18, 20, 23 | mpbir2an 944 | 
. . . . . . . . 9
⊢ ∅
∈ 𝐴 | 
| 25 |   | eleq2 2260 | 
. . . . . . . . 9
⊢ (𝑧 = 𝐴 → (∅ ∈ 𝑧 ↔ ∅ ∈ 𝐴)) | 
| 26 | 24, 25 | mpbiri 168 | 
. . . . . . . 8
⊢ (𝑧 = 𝐴 → ∅ ∈ 𝑧) | 
| 27 |   | elex2 2779 | 
. . . . . . . 8
⊢ (∅
∈ 𝑧 →
∃𝑤 𝑤 ∈ 𝑧) | 
| 28 | 26, 27 | syl 14 | 
. . . . . . 7
⊢ (𝑧 = 𝐴 → ∃𝑤 𝑤 ∈ 𝑧) | 
| 29 |   | p0ex 4221 | 
. . . . . . . . . . 11
⊢ {∅}
∈ V | 
| 30 | 29 | prid2 3729 | 
. . . . . . . . . 10
⊢ {∅}
∈ {∅, {∅}} | 
| 31 |   | eqid 2196 | 
. . . . . . . . . . 11
⊢ {∅}
= {∅} | 
| 32 | 31 | orci 732 | 
. . . . . . . . . 10
⊢
({∅} = {∅} ∨ 𝑦 = {∅}) | 
| 33 |   | eqeq1 2203 | 
. . . . . . . . . . . 12
⊢ (𝑥 = {∅} → (𝑥 = {∅} ↔ {∅} =
{∅})) | 
| 34 | 33 | orbi1d 792 | 
. . . . . . . . . . 11
⊢ (𝑥 = {∅} → ((𝑥 = {∅} ∨ 𝑦 = {∅}) ↔ ({∅}
= {∅} ∨ 𝑦 =
{∅}))) | 
| 35 | 34, 7 | elrab2 2923 | 
. . . . . . . . . 10
⊢
({∅} ∈ 𝐵
↔ ({∅} ∈ {∅, {∅}} ∧ ({∅} = {∅} ∨
𝑦 =
{∅}))) | 
| 36 | 30, 32, 35 | mpbir2an 944 | 
. . . . . . . . 9
⊢ {∅}
∈ 𝐵 | 
| 37 |   | eleq2 2260 | 
. . . . . . . . 9
⊢ (𝑧 = 𝐵 → ({∅} ∈ 𝑧 ↔ {∅} ∈ 𝐵)) | 
| 38 | 36, 37 | mpbiri 168 | 
. . . . . . . 8
⊢ (𝑧 = 𝐵 → {∅} ∈ 𝑧) | 
| 39 |   | elex2 2779 | 
. . . . . . . 8
⊢
({∅} ∈ 𝑧
→ ∃𝑤 𝑤 ∈ 𝑧) | 
| 40 | 38, 39 | syl 14 | 
. . . . . . 7
⊢ (𝑧 = 𝐵 → ∃𝑤 𝑤 ∈ 𝑧) | 
| 41 | 28, 40 | jaoi 717 | 
. . . . . 6
⊢ ((𝑧 = 𝐴 ∨ 𝑧 = 𝐵) → ∃𝑤 𝑤 ∈ 𝑧) | 
| 42 | 15, 16, 41 | 3syl 17 | 
. . . . 5
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ 𝑧 ∈ 𝐶) → ∃𝑤 𝑤 ∈ 𝑧) | 
| 43 | 42 | ralrimiva 2570 | 
. . . 4
⊢
((CHOICE ∧ 𝑦 ⊆ {∅}) → ∀𝑧 ∈ 𝐶 ∃𝑤 𝑤 ∈ 𝑧) | 
| 44 | 1, 13, 43 | acfun 7274 | 
. . 3
⊢
((CHOICE ∧ 𝑦 ⊆ {∅}) → ∃𝑓(𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) | 
| 45 |   | 0nep0 4198 | 
. . . . . . . . . 10
⊢ ∅
≠ {∅} | 
| 46 | 45 | neii 2369 | 
. . . . . . . . 9
⊢  ¬
∅ = {∅} | 
| 47 |   | simplr 528 | 
. . . . . . . . . 10
⊢
(((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) ∧ (𝑓‘𝐵) = {∅}) → (𝑓‘𝐴) = ∅) | 
| 48 |   | simpr 110 | 
. . . . . . . . . 10
⊢
(((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) ∧ (𝑓‘𝐵) = {∅}) → (𝑓‘𝐵) = {∅}) | 
| 49 | 47, 48 | eqeq12d 2211 | 
. . . . . . . . 9
⊢
(((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) ∧ (𝑓‘𝐵) = {∅}) → ((𝑓‘𝐴) = (𝑓‘𝐵) ↔ ∅ =
{∅})) | 
| 50 | 46, 49 | mtbiri 676 | 
. . . . . . . 8
⊢
(((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) ∧ (𝑓‘𝐵) = {∅}) → ¬ (𝑓‘𝐴) = (𝑓‘𝐵)) | 
| 51 |   | olc 712 | 
. . . . . . . . . . . . 13
⊢ (𝑦 = {∅} → (𝑥 = ∅ ∨ 𝑦 = {∅})) | 
| 52 | 51 | ralrimivw 2571 | 
. . . . . . . . . . . 12
⊢ (𝑦 = {∅} →
∀𝑥 ∈ {∅,
{∅}} (𝑥 = ∅
∨ 𝑦 =
{∅})) | 
| 53 |   | rabid2 2674 | 
. . . . . . . . . . . 12
⊢
({∅, {∅}} = {𝑥 ∈ {∅, {∅}} ∣ (𝑥 = ∅ ∨ 𝑦 = {∅})} ↔
∀𝑥 ∈ {∅,
{∅}} (𝑥 = ∅
∨ 𝑦 =
{∅})) | 
| 54 | 52, 53 | sylibr 134 | 
. . . . . . . . . . 11
⊢ (𝑦 = {∅} → {∅,
{∅}} = {𝑥 ∈
{∅, {∅}} ∣ (𝑥 = ∅ ∨ 𝑦 = {∅})}) | 
| 55 | 54, 3 | eqtr4di 2247 | 
. . . . . . . . . 10
⊢ (𝑦 = {∅} → {∅,
{∅}} = 𝐴) | 
| 56 |   | olc 712 | 
. . . . . . . . . . . . 13
⊢ (𝑦 = {∅} → (𝑥 = {∅} ∨ 𝑦 = {∅})) | 
| 57 | 56 | ralrimivw 2571 | 
. . . . . . . . . . . 12
⊢ (𝑦 = {∅} →
∀𝑥 ∈ {∅,
{∅}} (𝑥 = {∅}
∨ 𝑦 =
{∅})) | 
| 58 |   | rabid2 2674 | 
. . . . . . . . . . . 12
⊢
({∅, {∅}} = {𝑥 ∈ {∅, {∅}} ∣ (𝑥 = {∅} ∨ 𝑦 = {∅})} ↔
∀𝑥 ∈ {∅,
{∅}} (𝑥 = {∅}
∨ 𝑦 =
{∅})) | 
| 59 | 57, 58 | sylibr 134 | 
. . . . . . . . . . 11
⊢ (𝑦 = {∅} → {∅,
{∅}} = {𝑥 ∈
{∅, {∅}} ∣ (𝑥 = {∅} ∨ 𝑦 = {∅})}) | 
| 60 | 59, 7 | eqtr4di 2247 | 
. . . . . . . . . 10
⊢ (𝑦 = {∅} → {∅,
{∅}} = 𝐵) | 
| 61 | 55, 60 | eqtr3d 2231 | 
. . . . . . . . 9
⊢ (𝑦 = {∅} → 𝐴 = 𝐵) | 
| 62 | 61 | fveq2d 5562 | 
. . . . . . . 8
⊢ (𝑦 = {∅} → (𝑓‘𝐴) = (𝑓‘𝐵)) | 
| 63 | 50, 62 | nsyl 629 | 
. . . . . . 7
⊢
(((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) ∧ (𝑓‘𝐵) = {∅}) → ¬ 𝑦 = {∅}) | 
| 64 | 63 | olcd 735 | 
. . . . . 6
⊢
(((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) ∧ (𝑓‘𝐵) = {∅}) → (𝑦 = {∅} ∨ ¬ 𝑦 = {∅})) | 
| 65 |   | simpr 110 | 
. . . . . . 7
⊢
(((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) ∧ 𝑦 = {∅}) → 𝑦 = {∅}) | 
| 66 | 65 | orcd 734 | 
. . . . . 6
⊢
(((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) ∧ 𝑦 = {∅}) → (𝑦 = {∅} ∨ ¬ 𝑦 = {∅})) | 
| 67 |   | fveq2 5558 | 
. . . . . . . . . . 11
⊢ (𝑧 = 𝐵 → (𝑓‘𝑧) = (𝑓‘𝐵)) | 
| 68 |   | id 19 | 
. . . . . . . . . . 11
⊢ (𝑧 = 𝐵 → 𝑧 = 𝐵) | 
| 69 | 67, 68 | eleq12d 2267 | 
. . . . . . . . . 10
⊢ (𝑧 = 𝐵 → ((𝑓‘𝑧) ∈ 𝑧 ↔ (𝑓‘𝐵) ∈ 𝐵)) | 
| 70 |   | simprr 531 | 
. . . . . . . . . 10
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧) | 
| 71 | 9 | prid2 3729 | 
. . . . . . . . . . . 12
⊢ 𝐵 ∈ {𝐴, 𝐵} | 
| 72 | 71, 2 | eleqtrri 2272 | 
. . . . . . . . . . 11
⊢ 𝐵 ∈ 𝐶 | 
| 73 | 72 | a1i 9 | 
. . . . . . . . . 10
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → 𝐵 ∈ 𝐶) | 
| 74 | 69, 70, 73 | rspcdva 2873 | 
. . . . . . . . 9
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → (𝑓‘𝐵) ∈ 𝐵) | 
| 75 |   | eqeq1 2203 | 
. . . . . . . . . . 11
⊢ (𝑥 = (𝑓‘𝐵) → (𝑥 = {∅} ↔ (𝑓‘𝐵) = {∅})) | 
| 76 | 75 | orbi1d 792 | 
. . . . . . . . . 10
⊢ (𝑥 = (𝑓‘𝐵) → ((𝑥 = {∅} ∨ 𝑦 = {∅}) ↔ ((𝑓‘𝐵) = {∅} ∨ 𝑦 = {∅}))) | 
| 77 | 76, 7 | elrab2 2923 | 
. . . . . . . . 9
⊢ ((𝑓‘𝐵) ∈ 𝐵 ↔ ((𝑓‘𝐵) ∈ {∅, {∅}} ∧ ((𝑓‘𝐵) = {∅} ∨ 𝑦 = {∅}))) | 
| 78 | 74, 77 | sylib 122 | 
. . . . . . . 8
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → ((𝑓‘𝐵) ∈ {∅, {∅}} ∧ ((𝑓‘𝐵) = {∅} ∨ 𝑦 = {∅}))) | 
| 79 | 78 | simprd 114 | 
. . . . . . 7
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → ((𝑓‘𝐵) = {∅} ∨ 𝑦 = {∅})) | 
| 80 | 79 | adantr 276 | 
. . . . . 6
⊢
((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) → ((𝑓‘𝐵) = {∅} ∨ 𝑦 = {∅})) | 
| 81 | 64, 66, 80 | mpjaodan 799 | 
. . . . 5
⊢
((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) → (𝑦 = {∅} ∨ ¬ 𝑦 = {∅})) | 
| 82 |   | df-dc 836 | 
. . . . 5
⊢
(DECID 𝑦 = {∅} ↔ (𝑦 = {∅} ∨ ¬ 𝑦 = {∅})) | 
| 83 | 81, 82 | sylibr 134 | 
. . . 4
⊢
((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ (𝑓‘𝐴) = ∅) → DECID
𝑦 =
{∅}) | 
| 84 |   | simpr 110 | 
. . . . . 6
⊢
((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ 𝑦 = {∅}) → 𝑦 = {∅}) | 
| 85 | 84 | orcd 734 | 
. . . . 5
⊢
((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ 𝑦 = {∅}) → (𝑦 = {∅} ∨ ¬ 𝑦 = {∅})) | 
| 86 | 85, 82 | sylibr 134 | 
. . . 4
⊢
((((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) ∧ 𝑦 = {∅}) → DECID
𝑦 =
{∅}) | 
| 87 |   | fveq2 5558 | 
. . . . . . . 8
⊢ (𝑧 = 𝐴 → (𝑓‘𝑧) = (𝑓‘𝐴)) | 
| 88 |   | id 19 | 
. . . . . . . 8
⊢ (𝑧 = 𝐴 → 𝑧 = 𝐴) | 
| 89 | 87, 88 | eleq12d 2267 | 
. . . . . . 7
⊢ (𝑧 = 𝐴 → ((𝑓‘𝑧) ∈ 𝑧 ↔ (𝑓‘𝐴) ∈ 𝐴)) | 
| 90 | 6 | prid1 3728 | 
. . . . . . . . 9
⊢ 𝐴 ∈ {𝐴, 𝐵} | 
| 91 | 90, 2 | eleqtrri 2272 | 
. . . . . . . 8
⊢ 𝐴 ∈ 𝐶 | 
| 92 | 91 | a1i 9 | 
. . . . . . 7
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → 𝐴 ∈ 𝐶) | 
| 93 | 89, 70, 92 | rspcdva 2873 | 
. . . . . 6
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → (𝑓‘𝐴) ∈ 𝐴) | 
| 94 |   | eqeq1 2203 | 
. . . . . . . 8
⊢ (𝑥 = (𝑓‘𝐴) → (𝑥 = ∅ ↔ (𝑓‘𝐴) = ∅)) | 
| 95 | 94 | orbi1d 792 | 
. . . . . . 7
⊢ (𝑥 = (𝑓‘𝐴) → ((𝑥 = ∅ ∨ 𝑦 = {∅}) ↔ ((𝑓‘𝐴) = ∅ ∨ 𝑦 = {∅}))) | 
| 96 | 95, 3 | elrab2 2923 | 
. . . . . 6
⊢ ((𝑓‘𝐴) ∈ 𝐴 ↔ ((𝑓‘𝐴) ∈ {∅, {∅}} ∧ ((𝑓‘𝐴) = ∅ ∨ 𝑦 = {∅}))) | 
| 97 | 93, 96 | sylib 122 | 
. . . . 5
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → ((𝑓‘𝐴) ∈ {∅, {∅}} ∧ ((𝑓‘𝐴) = ∅ ∨ 𝑦 = {∅}))) | 
| 98 | 97 | simprd 114 | 
. . . 4
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → ((𝑓‘𝐴) = ∅ ∨ 𝑦 = {∅})) | 
| 99 | 83, 86, 98 | mpjaodan 799 | 
. . 3
⊢
(((CHOICE ∧ 𝑦 ⊆ {∅}) ∧ (𝑓 Fn 𝐶 ∧ ∀𝑧 ∈ 𝐶 (𝑓‘𝑧) ∈ 𝑧)) → DECID 𝑦 = {∅}) | 
| 100 | 44, 99 | exlimddv 1913 | 
. 2
⊢
((CHOICE ∧ 𝑦 ⊆ {∅}) →
DECID 𝑦 =
{∅}) | 
| 101 | 100 | exmid1dc 4233 | 
1
⊢
(CHOICE → EXMID) |