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Theorem uniex2 4531
Description: The Axiom of Union using the standard abbreviation for union. Given any set  x, its union  y exists. (Contributed by NM, 4-Jun-2006.)
Assertion
Ref Expression
uniex2  |-  E. y 
y  =  U. x
Distinct variable group:    x, y

Proof of Theorem uniex2
Dummy variable  z is distinct from all other variables.
StepHypRef Expression
1 zfun 4529 . . . 4  |-  E. y A. z ( E. y
( z  e.  y  /\  y  e.  x
)  ->  z  e.  y )
2 eluni 3846 . . . . . . 7  |-  ( z  e.  U. x  <->  E. y
( z  e.  y  /\  y  e.  x
) )
32imbi1i 315 . . . . . 6  |-  ( ( z  e.  U. x  ->  z  e.  y )  <-> 
( E. y ( z  e.  y  /\  y  e.  x )  ->  z  e.  y ) )
43albii 1556 . . . . 5  |-  ( A. z ( z  e. 
U. x  ->  z  e.  y )  <->  A. z
( E. y ( z  e.  y  /\  y  e.  x )  ->  z  e.  y ) )
54exbii 1572 . . . 4  |-  ( E. y A. z ( z  e.  U. x  ->  z  e.  y )  <->  E. y A. z ( E. y ( z  e.  y  /\  y  e.  x )  ->  z  e.  y ) )
61, 5mpbir 200 . . 3  |-  E. y A. z ( z  e. 
U. x  ->  z  e.  y )
76bm1.3ii 4160 . 2  |-  E. y A. z ( z  e.  y  <->  z  e.  U. x )
8 dfcleq 2290 . . 3  |-  ( y  =  U. x  <->  A. z
( z  e.  y  <-> 
z  e.  U. x
) )
98exbii 1572 . 2  |-  ( E. y  y  =  U. x 
<->  E. y A. z
( z  e.  y  <-> 
z  e.  U. x
) )
107, 9mpbir 200 1  |-  E. y 
y  =  U. x
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 176    /\ wa 358   A.wal 1530   E.wex 1531    = wceq 1632    e. wcel 1696   U.cuni 3843
This theorem is referenced by:  uniex  4532
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1536  ax-5 1547  ax-17 1606  ax-9 1644  ax-8 1661  ax-13 1698  ax-14 1700  ax-6 1715  ax-7 1720  ax-11 1727  ax-12 1878  ax-ext 2277  ax-sep 4157  ax-un 4528
This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-tru 1310  df-ex 1532  df-nf 1535  df-sb 1639  df-clab 2283  df-cleq 2289  df-clel 2292  df-nfc 2421  df-v 2803  df-uni 3844
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