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Theorem class2set 4558
Description: Construct, from any class  A, a set equal to it when the class exists and equal to the empty set when the class is proper. This theorem shows that the constructed set always exists. (Contributed by NM, 16-Oct-2003.)
Assertion
Ref Expression
class2set  |-  { x  e.  A  |  A  e.  _V }  e.  _V
Distinct variable group:    x, A

Proof of Theorem class2set
StepHypRef Expression
1 rabexg 4541 . 2  |-  ( A  e.  _V  ->  { x  e.  A  |  A  e.  _V }  e.  _V )
2 simpl 455 . . . . 5  |-  ( ( -.  A  e.  _V  /\  x  e.  A )  ->  -.  A  e.  _V )
32nrexdv 2857 . . . 4  |-  ( -.  A  e.  _V  ->  -. 
E. x  e.  A  A  e.  _V )
4 rabn0 3756 . . . . 5  |-  ( { x  e.  A  |  A  e.  _V }  =/=  (/)  <->  E. x  e.  A  A  e.  _V )
54necon1bbii 2665 . . . 4  |-  ( -. 
E. x  e.  A  A  e.  _V  <->  { x  e.  A  |  A  e.  _V }  =  (/) )
63, 5sylib 196 . . 3  |-  ( -.  A  e.  _V  ->  { x  e.  A  |  A  e.  _V }  =  (/) )
7 0ex 4523 . . 3  |-  (/)  e.  _V
86, 7syl6eqel 2496 . 2  |-  ( -.  A  e.  _V  ->  { x  e.  A  |  A  e.  _V }  e.  _V )
91, 8pm2.61i 164 1  |-  { x  e.  A  |  A  e.  _V }  e.  _V
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    = wceq 1403    e. wcel 1840   E.wrex 2752   {crab 2755   _Vcvv 3056   (/)c0 3735
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1637  ax-4 1650  ax-5 1723  ax-6 1769  ax-7 1812  ax-10 1859  ax-11 1864  ax-12 1876  ax-13 2024  ax-ext 2378  ax-sep 4514  ax-nul 4522
This theorem depends on definitions:  df-bi 185  df-or 368  df-an 369  df-tru 1406  df-ex 1632  df-nf 1636  df-sb 1762  df-clab 2386  df-cleq 2392  df-clel 2395  df-nfc 2550  df-ne 2598  df-ral 2756  df-rex 2757  df-rab 2760  df-v 3058  df-dif 3414  df-in 3418  df-ss 3425  df-nul 3736
This theorem is referenced by: (None)
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