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Metamath Proof Explorer

Theorem unisnv

Description: A set equals the union of its singleton (setvar case). (Contributed by NM, 30-Aug-1993)

Ref Expression
Assertion unisnv 
|- U. { x } = x

Proof

Step Hyp Ref Expression
1 vex 
 |-  x e. _V
2 1 unisn 
 |-  U. { x } = x