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Theorem sspr 4366
Description: The subsets of a pair. (Contributed by NM, 16-Mar-2006.) (Proof shortened by Mario Carneiro, 2-Jul-2016.)
Assertion
Ref Expression
sspr  |-  ( A 
C_  { B ,  C }  <->  ( ( A  =  (/)  \/  A  =  { B } )  \/  ( A  =  { C }  \/  A  =  { B ,  C } ) ) )

Proof of Theorem sspr
StepHypRef Expression
1 uncom 3757 . . . . 5  |-  ( (/)  u. 
{ B ,  C } )  =  ( { B ,  C }  u.  (/) )
2 un0 3967 . . . . 5  |-  ( { B ,  C }  u.  (/) )  =  { B ,  C }
31, 2eqtri 2644 . . . 4  |-  ( (/)  u. 
{ B ,  C } )  =  { B ,  C }
43sseq2i 3630 . . 3  |-  ( A 
C_  ( (/)  u.  { B ,  C }
)  <->  A  C_  { B ,  C } )
5 0ss 3972 . . . 4  |-  (/)  C_  A
65biantrur 527 . . 3  |-  ( A 
C_  ( (/)  u.  { B ,  C }
)  <->  ( (/)  C_  A  /\  A  C_  ( (/)  u. 
{ B ,  C } ) ) )
74, 6bitr3i 266 . 2  |-  ( A 
C_  { B ,  C }  <->  ( (/)  C_  A  /\  A  C_  ( (/)  u. 
{ B ,  C } ) ) )
8 ssunpr 4365 . 2  |-  ( (
(/)  C_  A  /\  A  C_  ( (/)  u.  { B ,  C } ) )  <-> 
( ( A  =  (/)  \/  A  =  (
(/)  u.  { B } ) )  \/  ( A  =  (
(/)  u.  { C } )  \/  A  =  ( (/)  u.  { B ,  C }
) ) ) )
9 uncom 3757 . . . . . 6  |-  ( (/)  u. 
{ B } )  =  ( { B }  u.  (/) )
10 un0 3967 . . . . . 6  |-  ( { B }  u.  (/) )  =  { B }
119, 10eqtri 2644 . . . . 5  |-  ( (/)  u. 
{ B } )  =  { B }
1211eqeq2i 2634 . . . 4  |-  ( A  =  ( (/)  u.  { B } )  <->  A  =  { B } )
1312orbi2i 541 . . 3  |-  ( ( A  =  (/)  \/  A  =  ( (/)  u.  { B } ) )  <->  ( A  =  (/)  \/  A  =  { B } ) )
14 uncom 3757 . . . . . 6  |-  ( (/)  u. 
{ C } )  =  ( { C }  u.  (/) )
15 un0 3967 . . . . . 6  |-  ( { C }  u.  (/) )  =  { C }
1614, 15eqtri 2644 . . . . 5  |-  ( (/)  u. 
{ C } )  =  { C }
1716eqeq2i 2634 . . . 4  |-  ( A  =  ( (/)  u.  { C } )  <->  A  =  { C } )
183eqeq2i 2634 . . . 4  |-  ( A  =  ( (/)  u.  { B ,  C }
)  <->  A  =  { B ,  C }
)
1917, 18orbi12i 543 . . 3  |-  ( ( A  =  ( (/)  u. 
{ C } )  \/  A  =  (
(/)  u.  { B ,  C } ) )  <-> 
( A  =  { C }  \/  A  =  { B ,  C } ) )
2013, 19orbi12i 543 . 2  |-  ( ( ( A  =  (/)  \/  A  =  ( (/)  u. 
{ B } ) )  \/  ( A  =  ( (/)  u.  { C } )  \/  A  =  ( (/)  u.  { B ,  C }
) ) )  <->  ( ( A  =  (/)  \/  A  =  { B } )  \/  ( A  =  { C }  \/  A  =  { B ,  C } ) ) )
217, 8, 203bitri 286 1  |-  ( A 
C_  { B ,  C }  <->  ( ( A  =  (/)  \/  A  =  { B } )  \/  ( A  =  { C }  \/  A  =  { B ,  C } ) ) )
Colors of variables: wff setvar class
Syntax hints:    <-> wb 196    \/ wo 383    /\ wa 384    = wceq 1483    u. cun 3572    C_ wss 3574   (/)c0 3915   {csn 4177   {cpr 4179
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602
This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3an 1039  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ral 2917  df-v 3202  df-dif 3577  df-un 3579  df-in 3581  df-ss 3588  df-nul 3916  df-sn 4178  df-pr 4180
This theorem is referenced by:  sstp  4367  pwpr  4430  propssopi  4971  indistopon  20805
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