Theorem uniiun 3980

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 3851	. 2 |- U. A = { y | E. x e. A y e. x }
2		df-iun 3928	. 2 |- U_ x e. A x = { y | E. x e. A y e. x }
3	1, 2	eqtr4i 2228	1 |- U. A = U_ x e. A x

Syntax hints:   = wceq 1372   {cab 2190   E.wrex 2484   U.cuni 3849   U_ciun 3926

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 1469  ax-7 1470  ax-gen 1471  ax-ie1 1515  ax-ie2 1516  ax-8 1526  ax-11 1528  ax-4 1532  ax-17 1548  ax-i9 1552  ax-ial 1556  ax-i5r 1557  ax-ext 2186

This theorem depends on definitions:  df-bi 117  df-tru 1375  df-nf 1483  df-sb 1785  df-clab 2191  df-cleq 2197  df-rex 2489  df-uni 3850  df-iun 3928

This theorem is referenced by:  iunpwss  4018  truni  4155  iunpw  4526  reluni  4797  rnuni  5093  imauni  5829  hashuni  11764  tgidm  14517  unicld  14559  tgrest  14612  txbasval  14710