Database
ZF (ZERMELO-FRAENKEL) SET THEORY
ZF Set Theory - start with the Axiom of Extensionality
Unordered and ordered pairs
prnz
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prnzg
Metamath Proof Explorer
Ascii
Structured
Theorem
prnz
Description:
A pair containing a set is not empty.
(Contributed by
NM
, 9-Apr-1994)
Ref
Expression
Hypothesis
prnz.1
⊢
𝐴
∈ V
Assertion
prnz
⊢
{
𝐴
,
𝐵
} ≠ ∅
Proof
Step
Hyp
Ref
Expression
1
prnz.1
⊢
𝐴
∈ V
2
1
prid1
⊢
𝐴
∈ {
𝐴
,
𝐵
}
3
2
ne0ii
⊢
{
𝐴
,
𝐵
} ≠ ∅