New Foundations Explorer < Previous   Next > Nearby theorems Mirrors  >  Home  >  NFE Home  >  Th. List  >  dmun GIF version

Theorem dmun 4912
 Description: The domain of a union is the union of domains. Exercise 56(a) of [Enderton] p. 65. (The proof was shortened by Andrew Salmon, 27-Aug-2011.) (Contributed by set.mm contributors, 12-Aug-1994.) (Revised by set.mm contributors, 27-Aug-2011.)
Assertion
Ref Expression
dmun dom (AB) = (dom A ∪ dom B)

Proof of Theorem dmun
Dummy variables x y are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 dfdm3 4901 . 2 dom (AB) = {x yx, y (AB)}
2 eldm 4898 . . . . 5 (x dom Ay xAy)
3 eldm 4898 . . . . 5 (x dom By xBy)
42, 3orbi12i 507 . . . 4 ((x dom A x dom B) ↔ (y xAy y xBy))
5 elun 3220 . . . 4 (x (dom A ∪ dom B) ↔ (x dom A x dom B))
6 df-br 4640 . . . . . . 7 (x(AB)yx, y (AB))
7 brun 4692 . . . . . . 7 (x(AB)y ↔ (xAy xBy))
86, 7bitr3i 242 . . . . . 6 (x, y (AB) ↔ (xAy xBy))
98exbii 1582 . . . . 5 (yx, y (AB) ↔ y(xAy xBy))
10 19.43 1605 . . . . 5 (y(xAy xBy) ↔ (y xAy y xBy))
119, 10bitri 240 . . . 4 (yx, y (AB) ↔ (y xAy y xBy))
124, 5, 113bitr4i 268 . . 3 (x (dom A ∪ dom B) ↔ yx, y (AB))
1312abbi2i 2464 . 2 (dom A ∪ dom B) = {x yx, y (AB)}
141, 13eqtr4i 2376 1 dom (AB) = (dom A ∪ dom B)
 Colors of variables: wff setvar class Syntax hints:   ∨ wo 357  ∃wex 1541   = wceq 1642   ∈ wcel 1710  {cab 2339   ∪ cun 3207  ⟨cop 4561   class class class wbr 4639  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-ima 4727  df-cnv 4785  df-rn 4786  df-dm 4787 This theorem is referenced by:  rnun  5036  dmpropg  5068  dmtpop  5071  fnun  5189
 Copyright terms: Public domain W3C validator