Proof of Theorem acexmidlemab
| Step | Hyp | Ref
 | Expression | 
| 1 |   | noel 3454 | 
. . . 4
⊢  ¬
∅ ∈ ∅ | 
| 2 |   | 0ex 4160 | 
. . . . . 6
⊢ ∅
∈ V | 
| 3 | 2 | snid 3653 | 
. . . . 5
⊢ ∅
∈ {∅} | 
| 4 |   | eleq2 2260 | 
. . . . 5
⊢ (∅
= {∅} → (∅ ∈ ∅ ↔ ∅ ∈
{∅})) | 
| 5 | 3, 4 | mpbiri 168 | 
. . . 4
⊢ (∅
= {∅} → ∅ ∈ ∅) | 
| 6 | 1, 5 | mto 663 | 
. . 3
⊢  ¬
∅ = {∅} | 
| 7 |   | acexmidlem.a | 
. . . . . . . . . 10
⊢ 𝐴 = {𝑥 ∈ {∅, {∅}} ∣ (𝑥 = ∅ ∨ 𝜑)} | 
| 8 |   | acexmidlem.b | 
. . . . . . . . . 10
⊢ 𝐵 = {𝑥 ∈ {∅, {∅}} ∣ (𝑥 = {∅} ∨ 𝜑)} | 
| 9 |   | acexmidlem.c | 
. . . . . . . . . 10
⊢ 𝐶 = {𝐴, 𝐵} | 
| 10 | 7, 8, 9 | acexmidlemph 5915 | 
. . . . . . . . 9
⊢ (𝜑 → 𝐴 = 𝐵) | 
| 11 |   | id 19 | 
. . . . . . . . . 10
⊢ (𝐴 = 𝐵 → 𝐴 = 𝐵) | 
| 12 |   | eleq1 2259 | 
. . . . . . . . . . . 12
⊢ (𝐴 = 𝐵 → (𝐴 ∈ 𝑢 ↔ 𝐵 ∈ 𝑢)) | 
| 13 | 12 | anbi1d 465 | 
. . . . . . . . . . 11
⊢ (𝐴 = 𝐵 → ((𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢) ↔ (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢))) | 
| 14 | 13 | rexbidv 2498 | 
. . . . . . . . . 10
⊢ (𝐴 = 𝐵 → (∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢) ↔ ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢))) | 
| 15 | 11, 14 | riotaeqbidv 5880 | 
. . . . . . . . 9
⊢ (𝐴 = 𝐵 → (℩𝑣 ∈ 𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢))) | 
| 16 | 10, 15 | syl 14 | 
. . . . . . . 8
⊢ (𝜑 → (℩𝑣 ∈ 𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢))) | 
| 17 | 16 | eqeq1d 2205 | 
. . . . . . 7
⊢ (𝜑 → ((℩𝑣 ∈ 𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅ ↔ (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅)) | 
| 18 | 17 | biimpa 296 | 
. . . . . 6
⊢ ((𝜑 ∧ (℩𝑣 ∈ 𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅) → (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅) | 
| 19 | 18 | adantrr 479 | 
. . . . 5
⊢ ((𝜑 ∧ ((℩𝑣 ∈ 𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅ ∧ (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = {∅})) → (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅) | 
| 20 |   | simprr 531 | 
. . . . 5
⊢ ((𝜑 ∧ ((℩𝑣 ∈ 𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅ ∧ (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = {∅})) → (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = {∅}) | 
| 21 | 19, 20 | eqtr3d 2231 | 
. . . 4
⊢ ((𝜑 ∧ ((℩𝑣 ∈ 𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅ ∧ (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = {∅})) → ∅ =
{∅}) | 
| 22 | 21 | ex 115 | 
. . 3
⊢ (𝜑 → (((℩𝑣 ∈ 𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅ ∧ (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = {∅}) → ∅ =
{∅})) | 
| 23 | 6, 22 | mtoi 665 | 
. 2
⊢ (𝜑 → ¬
((℩𝑣 ∈
𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅ ∧ (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = {∅})) | 
| 24 | 23 | con2i 628 | 
1
⊢
(((℩𝑣
∈ 𝐴 ∃𝑢 ∈ 𝑦 (𝐴 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = ∅ ∧ (℩𝑣 ∈ 𝐵 ∃𝑢 ∈ 𝑦 (𝐵 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢)) = {∅}) → ¬ 𝜑) |