Theorem nfeudv 2012

Description: Deduction version of nfeu 2016. Similar to nfeud 2013 but has the additional constraint that 𝑥 and 𝑦 must be distinct. (Contributed by Jim Kingdon, 25-May-2018.)

Hypotheses

Ref	Expression
nfeudv.1	⊢ Ⅎ𝑦𝜑
nfeudv.2	⊢ (𝜑 → Ⅎ𝑥𝜓)

Assertion

Ref	Expression
nfeudv	⊢ (𝜑 → Ⅎ𝑥∃!𝑦𝜓)

Distinct variable group:   𝑥,𝑦

Allowed substitution hints:   𝜑(𝑥,𝑦)   𝜓(𝑥,𝑦)

Proof of Theorem nfeudv

Dummy variable 𝑧 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		nfv 1508	. . 3 ⊢ Ⅎ𝑧𝜑
2		nfeudv.1	. . . 4 ⊢ Ⅎ𝑦𝜑
3		nfeudv.2	. . . . 5 ⊢ (𝜑 → Ⅎ𝑥𝜓)
4		nfv 1508	. . . . . 6 ⊢ Ⅎ𝑥 𝑦 = 𝑧
5	4	a1i 9	. . . . 5 ⊢ (𝜑 → Ⅎ𝑥 𝑦 = 𝑧)
6	3, 5	nfbid 1567	. . . 4 ⊢ (𝜑 → Ⅎ𝑥(𝜓 ↔ 𝑦 = 𝑧))
7	2, 6	nfald 1733	. . 3 ⊢ (𝜑 → Ⅎ𝑥∀𝑦(𝜓 ↔ 𝑦 = 𝑧))
8	1, 7	nfexd 1734	. 2 ⊢ (𝜑 → Ⅎ𝑥∃𝑧∀𝑦(𝜓 ↔ 𝑦 = 𝑧))
9		df-eu 2000	. . 3 ⊢ (∃!𝑦𝜓 ↔ ∃𝑧∀𝑦(𝜓 ↔ 𝑦 = 𝑧))
10	9	nfbii 1449	. 2 ⊢ (Ⅎ𝑥∃!𝑦𝜓 ↔ Ⅎ𝑥∃𝑧∀𝑦(𝜓 ↔ 𝑦 = 𝑧))
11	8, 10	sylibr 133	1 ⊢ (𝜑 → Ⅎ𝑥∃!𝑦𝜓)

Syntax hints:   → wi 4   ↔ wb 104  ∀wal 1329   = wceq 1331  Ⅎwnf 1436  ∃wex 1468  ∃!weu 1997

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1423  ax-7 1424  ax-gen 1425  ax-ie1 1469  ax-ie2 1470  ax-4 1487  ax-17 1506  ax-ial 1514  ax-i5r 1515

This theorem depends on definitions:  df-bi 116  df-nf 1437  df-eu 2000

This theorem is referenced by:  nfeud  2013