Theorem ideqg 4868

Description: For sets, the identity relation is the same as equality. (Contributed by NM, 30-Apr-2004.) (Revised by set.mm contributors, 27-Aug-2011.)

Assertion

Ref	Expression
ideqg	⊢ (B ∈ V → (A I B ↔ A = B))

Proof of Theorem ideqg

Dummy variables x y are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		brex 4689	. . 3 ⊢ (A I B → (A ∈ V ∧ B ∈ V))
2	1	adantl 452	. 2 ⊢ ((B ∈ V ∧ A I B) → (A ∈ V ∧ B ∈ V))
3		simpr 447	. . . 4 ⊢ ((B ∈ V ∧ A = B) → A = B)
4		elex 2867	. . . . 5 ⊢ (B ∈ V → B ∈ V)
5	4	adantr 451	. . . 4 ⊢ ((B ∈ V ∧ A = B) → B ∈ V)
6	3, 5	eqeltrd 2427	. . 3 ⊢ ((B ∈ V ∧ A = B) → A ∈ V)
7	6, 5	jca 518	. 2 ⊢ ((B ∈ V ∧ A = B) → (A ∈ V ∧ B ∈ V))
8		eqeq1 2359	. . 3 ⊢ (x = A → (x = y ↔ A = y))
9		eqeq2 2362	. . 3 ⊢ (y = B → (A = y ↔ A = B))
10		df-id 4767	. . 3 ⊢ I = {⟨x, y⟩ ∣ x = y}
11	8, 9, 10	brabg 4706	. 2 ⊢ ((A ∈ V ∧ B ∈ V) → (A I B ↔ A = B))
12	2, 7, 11	pm5.21nd 868	1 ⊢ (B ∈ V → (A I B ↔ A = B))

Syntax hints:   → wi 4   ↔ wb 176   ∧ wa 358   = wceq 1642   ∈ wcel 1710  Vcvv 2859   class class class wbr 4639   I cid 4763

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 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-id 4767

This theorem is referenced by:  ideq  4870  ididg  4871  brltc  6114