Theorem uniiun 4050

Description: Class union in terms of indexed union. Definition in [Stoll] p. 43. (Contributed by NM, 28-Jun-1998.)

Assertion

Ref	Expression
uniiun	|- U. A = U_ x e. A x

Distinct variable group:   x, A

Proof of Theorem uniiun

Dummy variable y is distinct from all other variables.

Step	Hyp	Ref	Expression
1		dfuni2 3921	. 2 |- U. A = { y | E. x e. A y e. x }
2		df-iun 3998	. 2 |- U_ x e. A x = { y | E. x e. A y e. x }
3	1, 2	eqtr4i 2258	1 |- U. A = U_ x e. A x

Syntax hints:   = wceq 1398   {cab 2220   E.wrex 2523   U.cuni 3919   U_ciun 3996

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1496  ax-7 1497  ax-gen 1498  ax-ie1 1542  ax-ie2 1543  ax-8 1553  ax-11 1555  ax-4 1559  ax-17 1575  ax-i9 1579  ax-ial 1583  ax-i5r 1584  ax-ext 2216

This theorem depends on definitions:  df-bi 117  df-tru 1401  df-nf 1510  df-sb 1812  df-clab 2221  df-cleq 2227  df-rex 2528  df-uni 3920  df-iun 3998

This theorem is referenced by:  iunpwss  4088  truni  4227  iunpw  4606  reluni  4880  rnuni  5179  imauni  5940  hashuni  12193  tgidm  15065  unicld  15107  tgrest  15160  txbasval  15258