Theorem equs5e 1809

Description: A property related to substitution that unlike equs5 1843 doesn't require a distinctor antecedent. (Contributed by NM, 2-Feb-2007.) (Revised by NM, 3-Feb-2015.)

Assertion

Ref	Expression
equs5e	⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜑) → ∀𝑥(𝑥 = 𝑦 → ∃𝑦𝜑))

Proof of Theorem equs5e

Step	Hyp	Ref	Expression
1		19.8a 1604	. . . . 5 ⊢ (𝜑 → ∃𝑦𝜑)
2		hbe1 1509	. . . . 5 ⊢ (∃𝑦𝜑 → ∀𝑦∃𝑦𝜑)
3	1, 2	syl 14	. . . 4 ⊢ (𝜑 → ∀𝑦∃𝑦𝜑)
4	3	anim2i 342	. . 3 ⊢ ((𝑥 = 𝑦 ∧ 𝜑) → (𝑥 = 𝑦 ∧ ∀𝑦∃𝑦𝜑))
5	4	eximi 1614	. 2 ⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜑) → ∃𝑥(𝑥 = 𝑦 ∧ ∀𝑦∃𝑦𝜑))
6		equs5a 1808	. 2 ⊢ (∃𝑥(𝑥 = 𝑦 ∧ ∀𝑦∃𝑦𝜑) → ∀𝑥(𝑥 = 𝑦 → ∃𝑦𝜑))
7	5, 6	syl 14	1 ⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜑) → ∀𝑥(𝑥 = 𝑦 → ∃𝑦𝜑))

Syntax hints:   → wi 4   ∧ wa 104  ∀wal 1362   = wceq 1364  ∃wex 1506

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1461  ax-gen 1463  ax-ie1 1507  ax-ie2 1508  ax-11 1520  ax-4 1524  ax-ial 1548

This theorem depends on definitions:  df-bi 117

This theorem is referenced by:  ax11e  1810  sb4e  1819