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Theorem eupth2lem1 16308
Description: Lemma for eupth2 . (Contributed by Mario Carneiro, 8-Apr-2015.)
Assertion
Ref Expression
eupth2lem1  |-  ( U  e.  V  ->  ( U  e.  if ( A  =  B ,  (/)
,  { A ,  B } )  <->  ( A  =/=  B  /\  ( U  =  A  \/  U  =  B ) ) ) )

Proof of Theorem eupth2lem1
StepHypRef Expression
1 elif 3617 . . 3  |-  ( U  e.  if ( A  =  B ,  (/) ,  { A ,  B } )  <->  ( ( A  =  B  /\  U  e.  (/) )  \/  ( -.  A  =  B  /\  U  e. 
{ A ,  B } ) ) )
2 noel 3498 . . . . 5  |-  -.  U  e.  (/)
32intnan 936 . . . 4  |-  -.  ( A  =  B  /\  U  e.  (/) )
4 biorf 751 . . . 4  |-  ( -.  ( A  =  B  /\  U  e.  (/) )  ->  ( ( -.  A  =  B  /\  U  e.  { A ,  B } )  <->  ( ( A  =  B  /\  U  e.  (/) )  \/  ( -.  A  =  B  /\  U  e. 
{ A ,  B } ) ) ) )
53, 4ax-mp 5 . . 3  |-  ( ( -.  A  =  B  /\  U  e.  { A ,  B }
)  <->  ( ( A  =  B  /\  U  e.  (/) )  \/  ( -.  A  =  B  /\  U  e.  { A ,  B } ) ) )
61, 5bitr4i 187 . 2  |-  ( U  e.  if ( A  =  B ,  (/) ,  { A ,  B } )  <->  ( -.  A  =  B  /\  U  e.  { A ,  B } ) )
7 df-ne 2403 . . . . 5  |-  ( A  =/=  B  <->  -.  A  =  B )
87bicomi 132 . . . 4  |-  ( -.  A  =  B  <->  A  =/=  B )
98a1i 9 . . 3  |-  ( U  e.  V  ->  ( -.  A  =  B  <->  A  =/=  B ) )
10 elprg 3689 . . 3  |-  ( U  e.  V  ->  ( U  e.  { A ,  B }  <->  ( U  =  A  \/  U  =  B ) ) )
119, 10anbi12d 473 . 2  |-  ( U  e.  V  ->  (
( -.  A  =  B  /\  U  e. 
{ A ,  B } )  <->  ( A  =/=  B  /\  ( U  =  A  \/  U  =  B ) ) ) )
126, 11bitrid 192 1  |-  ( U  e.  V  ->  ( U  e.  if ( A  =  B ,  (/)
,  { A ,  B } )  <->  ( A  =/=  B  /\  ( U  =  A  \/  U  =  B ) ) ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    /\ wa 104    <-> wb 105    \/ wo 715    = wceq 1397    e. wcel 2202    =/= wne 2402   (/)c0 3494   ifcif 3605   {cpr 3670
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-in1 619  ax-in2 620  ax-io 716  ax-5 1495  ax-7 1496  ax-gen 1497  ax-ie1 1541  ax-ie2 1542  ax-8 1552  ax-10 1553  ax-11 1554  ax-i12 1555  ax-bndl 1557  ax-4 1558  ax-17 1574  ax-i9 1578  ax-ial 1582  ax-i5r 1583  ax-ext 2213
This theorem depends on definitions:  df-bi 117  df-tru 1400  df-nf 1509  df-sb 1811  df-clab 2218  df-cleq 2224  df-clel 2227  df-nfc 2363  df-ne 2403  df-v 2804  df-dif 3202  df-un 3204  df-nul 3495  df-if 3606  df-sn 3675  df-pr 3676
This theorem is referenced by:  eupth2lem2dc  16309
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