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Database
ZF (ZERMELO-FRAENKEL) SET THEORY
ZF Set Theory - add the Axiom of Union
Schroeder-Bernstein Theorem
0domg
Metamath Proof Explorer
Description: Any set dominates the empty set. (Contributed by NM , 26-Oct-2003)
(Revised by Mario Carneiro , 26-Apr-2015) Avoid ax-pow , ax-un .
(Revised by BTernaryTau , 29-Nov-2024)
Ref
Expression
Assertion
0domg
⊢ A ∈ V → ∅ ≼ A
Proof
Step
Hyp
Ref
Expression
1
0ex
⊢ ∅ ∈ V
2
f1eq1
⊢ f = ∅ → f : ∅ ⟶ 1-1 A ↔ ∅ : ∅ ⟶ 1-1 A
3
f10
⊢ ∅ : ∅ ⟶ 1-1 A
4
1 2 3
ceqsexv2d
⊢ ∃ f f : ∅ ⟶ 1-1 A
5
brdom2g
⊢ ∅ ∈ V ∧ A ∈ V → ∅ ≼ A ↔ ∃ f f : ∅ ⟶ 1-1 A
6
1 5
mpan
⊢ A ∈ V → ∅ ≼ A ↔ ∃ f f : ∅ ⟶ 1-1 A
7
4 6
mpbiri
⊢ A ∈ V → ∅ ≼ A