Metamath Proof Explorer


Theorem unex

Description: The union of two sets is a set. Corollary 5.8 of TakeutiZaring p. 16. (Contributed by NM, 1-Jul-1994)

Ref Expression
Hypotheses unex.1 A V
unex.2 B V
Assertion unex A B V

Proof

Step Hyp Ref Expression
1 unex.1 A V
2 unex.2 B V
3 unexg A V B V A B V
4 1 2 3 mp2an A B V