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Theorem intmin 3708
Description: Any member of a class is the smallest of those members that include it. (Contributed by NM, 13-Aug-2002.) (Proof shortened by Andrew Salmon, 9-Jul-2011.)
Assertion
Ref Expression
intmin  |-  ( A  e.  B  ->  |^| { x  e.  B  |  A  C_  x }  =  A )
Distinct variable groups:    x, A    x, B

Proof of Theorem intmin
Dummy variable  y is distinct from all other variables.
StepHypRef Expression
1 vex 2622 . . . . 5  |-  y  e. 
_V
21elintrab 3700 . . . 4  |-  ( y  e.  |^| { x  e.  B  |  A  C_  x }  <->  A. x  e.  B  ( A  C_  x  -> 
y  e.  x ) )
3 ssid 3044 . . . . 5  |-  A  C_  A
4 sseq2 3048 . . . . . . 7  |-  ( x  =  A  ->  ( A  C_  x  <->  A  C_  A
) )
5 eleq2 2151 . . . . . . 7  |-  ( x  =  A  ->  (
y  e.  x  <->  y  e.  A ) )
64, 5imbi12d 232 . . . . . 6  |-  ( x  =  A  ->  (
( A  C_  x  ->  y  e.  x )  <-> 
( A  C_  A  ->  y  e.  A ) ) )
76rspcv 2718 . . . . 5  |-  ( A  e.  B  ->  ( A. x  e.  B  ( A  C_  x  -> 
y  e.  x )  ->  ( A  C_  A  ->  y  e.  A
) ) )
83, 7mpii 43 . . . 4  |-  ( A  e.  B  ->  ( A. x  e.  B  ( A  C_  x  -> 
y  e.  x )  ->  y  e.  A
) )
92, 8syl5bi 150 . . 3  |-  ( A  e.  B  ->  (
y  e.  |^| { x  e.  B  |  A  C_  x }  ->  y  e.  A ) )
109ssrdv 3031 . 2  |-  ( A  e.  B  ->  |^| { x  e.  B  |  A  C_  x }  C_  A
)
11 ssintub 3706 . . 3  |-  A  C_  |^|
{ x  e.  B  |  A  C_  x }
1211a1i 9 . 2  |-  ( A  e.  B  ->  A  C_ 
|^| { x  e.  B  |  A  C_  x }
)
1310, 12eqssd 3042 1  |-  ( A  e.  B  ->  |^| { x  e.  B  |  A  C_  x }  =  A )
Colors of variables: wff set class
Syntax hints:    -> wi 4    = wceq 1289    e. wcel 1438   A.wral 2359   {crab 2363    C_ wss 2999   |^|cint 3688
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-io 665  ax-5 1381  ax-7 1382  ax-gen 1383  ax-ie1 1427  ax-ie2 1428  ax-8 1440  ax-10 1441  ax-11 1442  ax-i12 1443  ax-bndl 1444  ax-4 1445  ax-17 1464  ax-i9 1468  ax-ial 1472  ax-i5r 1473  ax-ext 2070
This theorem depends on definitions:  df-bi 115  df-tru 1292  df-nf 1395  df-sb 1693  df-clab 2075  df-cleq 2081  df-clel 2084  df-nfc 2217  df-ral 2364  df-rab 2368  df-v 2621  df-in 3005  df-ss 3012  df-int 3689
This theorem is referenced by:  intmin2  3714  bm2.5ii  4313  onsucmin  4324
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