Metamath Proof Explorer


Theorem vsnex

Description: A singleton built on a setvar is a set. (Contributed by BJ, 15-Jan-2025)

Ref Expression
Assertion vsnex x V

Proof

Step Hyp Ref Expression
1 dfsn2 x = x x
2 zfpair2 x x V
3 1 2 eqeltri x V