Theorem coep 35868

Description: Composition with the membership relation. (Contributed by Scott Fenton, 18-Feb-2013.)

Hypotheses

Ref	Expression
coep.1	⊢ 𝐴 ∈ V
coep.2	⊢ 𝐵 ∈ V

Assertion

Ref	Expression
coep	⊢ (𝐴( E ∘ 𝑅)𝐵 ↔ ∃𝑥 ∈ 𝐵 𝐴𝑅𝑥)

Distinct variable groups:   𝑥,𝐴   𝑥,𝐵   𝑥,𝑅

Proof of Theorem coep

Step	Hyp	Ref	Expression
1		coep.2	. . . . 5 ⊢ 𝐵 ∈ V
2	1	epeli 5523	. . . 4 ⊢ (𝑥 E 𝐵 ↔ 𝑥 ∈ 𝐵)
3	2	anbi1ci 626	. . 3 ⊢ ((𝐴𝑅𝑥 ∧ 𝑥 E 𝐵) ↔ (𝑥 ∈ 𝐵 ∧ 𝐴𝑅𝑥))
4	3	exbii 1849	. 2 ⊢ (∃𝑥(𝐴𝑅𝑥 ∧ 𝑥 E 𝐵) ↔ ∃𝑥(𝑥 ∈ 𝐵 ∧ 𝐴𝑅𝑥))
5		coep.1	. . 3 ⊢ 𝐴 ∈ V
6	5, 1	brco 5816	. 2 ⊢ (𝐴( E ∘ 𝑅)𝐵 ↔ ∃𝑥(𝐴𝑅𝑥 ∧ 𝑥 E 𝐵))
7		df-rex 3058	. 2 ⊢ (∃𝑥 ∈ 𝐵 𝐴𝑅𝑥 ↔ ∃𝑥(𝑥 ∈ 𝐵 ∧ 𝐴𝑅𝑥))
8	4, 6, 7	3bitr4i 303	1 ⊢ (𝐴( E ∘ 𝑅)𝐵 ↔ ∃𝑥 ∈ 𝐵 𝐴𝑅𝑥)

Syntax hints:   ↔ wb 206   ∧ wa 395  ∃wex 1780   ∈ wcel 2113  ∃wrex 3057  Vcvv 3437   class class class wbr 5095   E cep 5520   ∘ ccom 5625

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796  ax-4 1810  ax-5 1911  ax-6 1968  ax-7 2009  ax-8 2115  ax-9 2123  ax-ext 2705  ax-sep 5238  ax-nul 5248  ax-pr 5374

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-3an 1088  df-tru 1544  df-fal 1554  df-ex 1781  df-sb 2068  df-clab 2712  df-cleq 2725  df-clel 2808  df-ne 2930  df-rex 3058  df-rab 3397  df-v 3439  df-dif 3901  df-un 3903  df-ss 3915  df-nul 4283  df-if 4477  df-sn 4578  df-pr 4580  df-op 4584  df-br 5096  df-opab 5158  df-eprel 5521  df-co 5630

This theorem is referenced by:  dffr5  35870  brbigcup  36012  elfuns  36029  brimage  36040