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Theorem xp1st 5874
Description: Location of the first element of a Cartesian product. (Contributed by Jeff Madsen, 2-Sep-2009.)
Assertion
Ref Expression
xp1st (𝐴 ∈ (𝐵 × 𝐶) → (1st𝐴) ∈ 𝐵)

Proof of Theorem xp1st
Dummy variables 𝑏 𝑐 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 elxp 4421 . 2 (𝐴 ∈ (𝐵 × 𝐶) ↔ ∃𝑏𝑐(𝐴 = ⟨𝑏, 𝑐⟩ ∧ (𝑏𝐵𝑐𝐶)))
2 vex 2617 . . . . . . 7 𝑏 ∈ V
3 vex 2617 . . . . . . 7 𝑐 ∈ V
42, 3op1std 5857 . . . . . 6 (𝐴 = ⟨𝑏, 𝑐⟩ → (1st𝐴) = 𝑏)
54eleq1d 2153 . . . . 5 (𝐴 = ⟨𝑏, 𝑐⟩ → ((1st𝐴) ∈ 𝐵𝑏𝐵))
65biimpar 291 . . . 4 ((𝐴 = ⟨𝑏, 𝑐⟩ ∧ 𝑏𝐵) → (1st𝐴) ∈ 𝐵)
76adantrr 463 . . 3 ((𝐴 = ⟨𝑏, 𝑐⟩ ∧ (𝑏𝐵𝑐𝐶)) → (1st𝐴) ∈ 𝐵)
87exlimivv 1821 . 2 (∃𝑏𝑐(𝐴 = ⟨𝑏, 𝑐⟩ ∧ (𝑏𝐵𝑐𝐶)) → (1st𝐴) ∈ 𝐵)
91, 8sylbi 119 1 (𝐴 ∈ (𝐵 × 𝐶) → (1st𝐴) ∈ 𝐵)
Colors of variables: wff set class
Syntax hints:  wi 4  wa 102   = wceq 1287  wex 1424  wcel 1436  cop 3428   × cxp 4402  cfv 4972  1st c1st 5847
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 663  ax-5 1379  ax-7 1380  ax-gen 1381  ax-ie1 1425  ax-ie2 1426  ax-8 1438  ax-10 1439  ax-11 1440  ax-i12 1441  ax-bndl 1442  ax-4 1443  ax-13 1447  ax-14 1448  ax-17 1462  ax-i9 1466  ax-ial 1470  ax-i5r 1471  ax-ext 2067  ax-sep 3925  ax-pow 3977  ax-pr 4003  ax-un 4227
This theorem depends on definitions:  df-bi 115  df-3an 924  df-tru 1290  df-nf 1393  df-sb 1690  df-eu 1948  df-mo 1949  df-clab 2072  df-cleq 2078  df-clel 2081  df-nfc 2214  df-ral 2360  df-rex 2361  df-v 2616  df-sbc 2829  df-un 2990  df-in 2992  df-ss 2999  df-pw 3411  df-sn 3431  df-pr 3432  df-op 3434  df-uni 3631  df-br 3815  df-opab 3869  df-mpt 3870  df-id 4087  df-xp 4410  df-rel 4411  df-cnv 4412  df-co 4413  df-dm 4414  df-rn 4415  df-iota 4937  df-fun 4974  df-fv 4980  df-1st 5849
This theorem is referenced by:  xpf1o  6493  xpmapenlem  6498  djuf1olem  6666  djur  6678  eldju1st  6683  dfplpq2  6834  dfmpq2  6835  enqbreq2  6837  enqdc1  6842  mulpipq2  6851  preqlu  6952  elnp1st2nd  6956  cauappcvgprlemladd  7138  elreal2  7289  cnref1o  9042  frecuzrdgrrn  9718  frec2uzrdg  9719  frecuzrdgrcl  9720  frecuzrdgsuc  9724  frecuzrdgrclt  9725  frecuzrdgg  9726  frecuzrdgsuctlem  9733  iseqvalt  9765  eucalgval  10830  eucalginv  10832  eucalglt  10833  eucialg  10835  sqpweven  10947  2sqpwodd  10948
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