Theorem bj-rexcom4bv 36877

Description: Version of rexcom4b 3514 and bj-rexcom4b 36878 with a disjoint variable condition on 𝑥, 𝑉, hence removing dependency on df-sb 2065 and df-clab 2715 (so that it depends on df-clel 2816 and df-rex 3071 only on top of first-order logic). Prefer its use over bj-rexcom4b 36878 when sufficient (in particular when 𝑉 is substituted for V). Note the 𝑉 in the hypothesis instead of V. (Contributed by BJ, 14-Sep-2019.) (Proof modification is discouraged.)

Hypothesis

Ref	Expression
bj-rexcom4bv.1	⊢ 𝐵 ∈ 𝑉

Assertion

Ref	Expression
bj-rexcom4bv	⊢ (∃𝑥∃𝑦 ∈ 𝐴 (𝜑 ∧ 𝑥 = 𝐵) ↔ ∃𝑦 ∈ 𝐴 𝜑)

Distinct variable groups:   𝑥,𝐴   𝑥,𝐵   𝑥,𝑉   𝑥,𝑦   𝜑,𝑥

Allowed substitution hints:   𝜑(𝑦)   𝐴(𝑦)   𝐵(𝑦)   𝑉(𝑦)

Proof of Theorem bj-rexcom4bv

Step	Hyp	Ref	Expression
1		rexcom4a 3292	. 2 ⊢ (∃𝑥∃𝑦 ∈ 𝐴 (𝜑 ∧ 𝑥 = 𝐵) ↔ ∃𝑦 ∈ 𝐴 (𝜑 ∧ ∃𝑥 𝑥 = 𝐵))
2		bj-rexcom4bv.1	. . . . 5 ⊢ 𝐵 ∈ 𝑉
3	2	bj-issetiv 36872	. . . 4 ⊢ ∃𝑥 𝑥 = 𝐵
4	3	biantru 529	. . 3 ⊢ (𝜑 ↔ (𝜑 ∧ ∃𝑥 𝑥 = 𝐵))
5	4	rexbii 3094	. 2 ⊢ (∃𝑦 ∈ 𝐴 𝜑 ↔ ∃𝑦 ∈ 𝐴 (𝜑 ∧ ∃𝑥 𝑥 = 𝐵))
6	1, 5	bitr4i 278	1 ⊢ (∃𝑥∃𝑦 ∈ 𝐴 (𝜑 ∧ 𝑥 = 𝐵) ↔ ∃𝑦 ∈ 𝐴 𝜑)

Syntax hints:   ↔ wb 206   ∧ wa 395   = wceq 1539  ∃wex 1778   ∈ wcel 2108  ∃wrex 3070

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1794  ax-4 1808  ax-5 1910  ax-6 1967  ax-7 2007  ax-8 2110  ax-11 2157

This theorem depends on definitions:  df-bi 207  df-an 396  df-ex 1779  df-clel 2816  df-rex 3071

This theorem is referenced by: (None)