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Theorem xp1st 5820
Description: Location of the first element of a Cartesian product. (Contributed by Jeff Madsen, 2-Sep-2009.)
Assertion
Ref Expression
xp1st  |-  ( A  e.  ( B  X.  C )  ->  ( 1st `  A )  e.  B )

Proof of Theorem xp1st
Dummy variables  b  c are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 elxp 4390 . 2  |-  ( A  e.  ( B  X.  C )  <->  E. b E. c ( A  = 
<. b ,  c >.  /\  ( b  e.  B  /\  c  e.  C
) ) )
2 vex 2577 . . . . . . 7  |-  b  e. 
_V
3 vex 2577 . . . . . . 7  |-  c  e. 
_V
42, 3op1std 5803 . . . . . 6  |-  ( A  =  <. b ,  c
>.  ->  ( 1st `  A
)  =  b )
54eleq1d 2122 . . . . 5  |-  ( A  =  <. b ,  c
>.  ->  ( ( 1st `  A )  e.  B  <->  b  e.  B ) )
65biimpar 285 . . . 4  |-  ( ( A  =  <. b ,  c >.  /\  b  e.  B )  ->  ( 1st `  A )  e.  B )
76adantrr 456 . . 3  |-  ( ( A  =  <. b ,  c >.  /\  (
b  e.  B  /\  c  e.  C )
)  ->  ( 1st `  A )  e.  B
)
87exlimivv 1792 . 2  |-  ( E. b E. c ( A  =  <. b ,  c >.  /\  (
b  e.  B  /\  c  e.  C )
)  ->  ( 1st `  A )  e.  B
)
91, 8sylbi 118 1  |-  ( A  e.  ( B  X.  C )  ->  ( 1st `  A )  e.  B )
Colors of variables: wff set class
Syntax hints:    -> wi 4    /\ wa 101    = wceq 1259   E.wex 1397    e. wcel 1409   <.cop 3406    X. cxp 4371   ` cfv 4930   1stc1st 5793
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105  ax-io 640  ax-5 1352  ax-7 1353  ax-gen 1354  ax-ie1 1398  ax-ie2 1399  ax-8 1411  ax-10 1412  ax-11 1413  ax-i12 1414  ax-bndl 1415  ax-4 1416  ax-13 1420  ax-14 1421  ax-17 1435  ax-i9 1439  ax-ial 1443  ax-i5r 1444  ax-ext 2038  ax-sep 3903  ax-pow 3955  ax-pr 3972  ax-un 4198
This theorem depends on definitions:  df-bi 114  df-3an 898  df-tru 1262  df-nf 1366  df-sb 1662  df-eu 1919  df-mo 1920  df-clab 2043  df-cleq 2049  df-clel 2052  df-nfc 2183  df-ral 2328  df-rex 2329  df-v 2576  df-sbc 2788  df-un 2950  df-in 2952  df-ss 2959  df-pw 3389  df-sn 3409  df-pr 3410  df-op 3412  df-uni 3609  df-br 3793  df-opab 3847  df-mpt 3848  df-id 4058  df-xp 4379  df-rel 4380  df-cnv 4381  df-co 4382  df-dm 4383  df-rn 4384  df-iota 4895  df-fun 4932  df-fv 4938  df-1st 5795
This theorem is referenced by:  dfplpq2  6510  dfmpq2  6511  enqbreq2  6513  enqdc1  6518  mulpipq2  6527  preqlu  6628  elnp1st2nd  6632  cauappcvgprlemladd  6814  elreal2  6965  cnref1o  8680  frecuzrdgrrn  9358
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