Theorem unexg 4101

Description: The union of two sets is a set. (Contributed by SF, 12-Jan-2015.)

Assertion

Ref	Expression
unexg	|- ((A e. V /\ B e. W) -> (A u. B) e. _V)

Proof of Theorem unexg

Step	Hyp	Ref	Expression
1		df-un 3214	. 2 |- (A u. B) = ( ∼ A &ncap ∼ B)
2		complexg 4099	. . 3 |- (A e. V -> ∼ A e. _V)
3		complexg 4099	. . 3 |- (B e. W -> ∼ B e. _V)
4		ninexg 4097	. . 3 |- (( ∼ A e. _V /\ ∼ B e. _V) -> ( ∼ A &ncap ∼ B) e. _V)
5	2, 3, 4	syl2an 463	. 2 |- ((A e. V /\ B e. W) -> ( ∼ A &ncap ∼ B) e. _V)
6	1, 5	syl5eqel 2437	1 |- ((A e. V /\ B e. W) -> (A u. B) e. _V)

Syntax hints:   -> wi 4   /\ wa 358   e. wcel 1710  _Vcvv 2859   &ncap cnin 3204   ∼ ccompl 3205   u. cun 3207

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334  ax-nin 4078

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2478  df-v 2861  df-nin 3211  df-compl 3212  df-un 3214

This theorem is referenced by:  symdifexg  4103  unex  4106  imakexg  4299  ncfindi  4475  opexg  4587  cupvalg  5812  fullfunexg  5859  addccan2nclem2  6264