Step |
Hyp |
Ref |
Expression |
1 |
|
dfac2a |
⊢ ( ∀ 𝑥 ∃ 𝑦 ∀ 𝑧 ∈ 𝑥 ( 𝑧 ≠ ∅ → ∃! 𝑣 ∈ 𝑧 ∃ 𝑢 ∈ 𝑦 ( 𝑧 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢 ) ) → CHOICE ) |
2 |
|
ac3 |
⊢ ∃ 𝑦 ∀ 𝑧 ∈ 𝑥 ( 𝑧 ≠ ∅ → ∃! 𝑣 ∈ 𝑧 ∃ 𝑢 ∈ 𝑦 ( 𝑧 ∈ 𝑢 ∧ 𝑣 ∈ 𝑢 ) ) |
3 |
1 2
|
mpg |
⊢ CHOICE |
4 |
|
dfackm |
⊢ ( CHOICE ↔ ∀ 𝑥 ∃ 𝑦 ∀ 𝑧 ∃ 𝑣 ∀ 𝑢 ( ( 𝑦 ∈ 𝑥 ∧ ( 𝑧 ∈ 𝑦 → ( ( 𝑣 ∈ 𝑥 ∧ ¬ 𝑦 = 𝑣 ) ∧ 𝑧 ∈ 𝑣 ) ) ) ∨ ( ¬ 𝑦 ∈ 𝑥 ∧ ( 𝑧 ∈ 𝑥 → ( ( 𝑣 ∈ 𝑧 ∧ 𝑣 ∈ 𝑦 ) ∧ ( ( 𝑢 ∈ 𝑧 ∧ 𝑢 ∈ 𝑦 ) → 𝑢 = 𝑣 ) ) ) ) ) ) |
5 |
3 4
|
mpbi |
⊢ ∀ 𝑥 ∃ 𝑦 ∀ 𝑧 ∃ 𝑣 ∀ 𝑢 ( ( 𝑦 ∈ 𝑥 ∧ ( 𝑧 ∈ 𝑦 → ( ( 𝑣 ∈ 𝑥 ∧ ¬ 𝑦 = 𝑣 ) ∧ 𝑧 ∈ 𝑣 ) ) ) ∨ ( ¬ 𝑦 ∈ 𝑥 ∧ ( 𝑧 ∈ 𝑥 → ( ( 𝑣 ∈ 𝑧 ∧ 𝑣 ∈ 𝑦 ) ∧ ( ( 𝑢 ∈ 𝑧 ∧ 𝑢 ∈ 𝑦 ) → 𝑢 = 𝑣 ) ) ) ) ) |
6 |
5
|
spi |
⊢ ∃ 𝑦 ∀ 𝑧 ∃ 𝑣 ∀ 𝑢 ( ( 𝑦 ∈ 𝑥 ∧ ( 𝑧 ∈ 𝑦 → ( ( 𝑣 ∈ 𝑥 ∧ ¬ 𝑦 = 𝑣 ) ∧ 𝑧 ∈ 𝑣 ) ) ) ∨ ( ¬ 𝑦 ∈ 𝑥 ∧ ( 𝑧 ∈ 𝑥 → ( ( 𝑣 ∈ 𝑧 ∧ 𝑣 ∈ 𝑦 ) ∧ ( ( 𝑢 ∈ 𝑧 ∧ 𝑢 ∈ 𝑦 ) → 𝑢 = 𝑣 ) ) ) ) ) |