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Theorem dfdm4 5507
 Description: Alternate definition of domain. (Contributed by SF, 23-Feb-2015.)
Assertion
Ref Expression
dfdm4 dom A = (1stA)

Proof of Theorem dfdm4
Dummy variables x y z are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 rexcom4 2878 . . . 4 (z A y z = x, yyz A z = x, y)
2 vex 2862 . . . . . 6 x V
32br1st 4858 . . . . 5 (z1st xy z = x, y)
43rexbii 2639 . . . 4 (z A z1st xz A y z = x, y)
5 risset 2661 . . . . 5 (x, y Az A z = x, y)
65exbii 1582 . . . 4 (yx, y Ayz A z = x, y)
71, 4, 63bitr4ri 269 . . 3 (yx, y Az A z1st x)
8 eldm2 4899 . . 3 (x dom Ayx, y A)
9 elima 4754 . . 3 (x (1stA) ↔ z A z1st x)
107, 8, 93bitr4i 268 . 2 (x dom Ax (1stA))
1110eqriv 2350 1 dom A = (1stA)
 Colors of variables: wff setvar class Syntax hints:  ∃wex 1541   = wceq 1642   ∈ wcel 1710  ∃wrex 2615  ⟨cop 4561   class class class wbr 4639  1st c1st 4717   “ cima 4722  dom cdm 4772 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-13 1712  ax-14 1714  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334  ax-nin 4078  ax-xp 4079  ax-cnv 4080  ax-1c 4081  ax-sset 4082  ax-si 4083  ax-ins2 4084  ax-ins3 4085  ax-typlower 4086  ax-sn 4087 This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-3or 935  df-3an 936  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-eu 2208  df-mo 2209  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2478  df-ne 2518  df-ral 2619  df-rex 2620  df-reu 2621  df-rmo 2622  df-rab 2623  df-v 2861  df-sbc 3047  df-nin 3211  df-compl 3212  df-in 3213  df-un 3214  df-dif 3215  df-symdif 3216  df-ss 3259  df-pss 3261  df-nul 3551  df-if 3663  df-pw 3724  df-sn 3741  df-pr 3742  df-uni 3892  df-int 3927  df-opk 4058  df-1c 4136  df-pw1 4137  df-uni1 4138  df-xpk 4185  df-cnvk 4186  df-ins2k 4187  df-ins3k 4188  df-imak 4189  df-cok 4190  df-p6 4191  df-sik 4192  df-ssetk 4193  df-imagek 4194  df-idk 4195  df-iota 4339  df-0c 4377  df-addc 4378  df-nnc 4379  df-fin 4380  df-lefin 4440  df-ltfin 4441  df-ncfin 4442  df-tfin 4443  df-evenfin 4444  df-oddfin 4445  df-sfin 4446  df-spfin 4447  df-phi 4565  df-op 4566  df-proj1 4567  df-proj2 4568  df-opab 4623  df-br 4640  df-1st 4723  df-ima 4727  df-cnv 4785  df-rn 4786  df-dm 4787 This theorem is referenced by:  fnsex  5832  mapexi  6003  fundmen  6043
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