Theorem eusvnf 4369

Description: Even if x is free in A, it is effectively bound when A ( x ) is single-valued. (Contributed by NM, 14-Oct-2010.) (Revised by Mario Carneiro, 14-Oct-2016.)

Assertion

Ref	Expression
eusvnf	|- ( E! y A. x y = A -> F/_ x A )

Distinct variable groups:   x, y   y, A

Allowed substitution hint:   A( x)

Proof of Theorem eusvnf

Dummy variables z w are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		euex 2027	. 2 |- ( E! y A. x y = A -> E. y A. x y = A )
2		vex 2684	. . . . . . 7 |- z e. _V
3		nfcv 2279	. . . . . . . 8 |- F/_ x z
4		nfcsb1v 3030	. . . . . . . . 9 |- F/_ x [_ z / x ]_ A
5	4	nfeq2 2291	. . . . . . . 8 |- F/ x y = [_ z / x ]_ A
6		csbeq1a 3007	. . . . . . . . 9 |- ( x = z -> A = [_ z / x ]_ A )
7	6	eqeq2d 2149	. . . . . . . 8 |- ( x = z -> ( y = A <-> y = [_ z / x ]_ A ) )
8	3, 5, 7	spcgf 2763	. . . . . . 7 |- ( z e. _V -> ( A. x y = A -> y = [_ z / x ]_ A ) )
9	2, 8	ax-mp 5	. . . . . 6 |- ( A. x y = A -> y = [_ z / x ]_ A )
10		vex 2684	. . . . . . 7 |- w e. _V
11		nfcv 2279	. . . . . . . 8 |- F/_ x w
12		nfcsb1v 3030	. . . . . . . . 9 |- F/_ x [_ w / x ]_ A
13	12	nfeq2 2291	. . . . . . . 8 |- F/ x y = [_ w / x ]_ A
14		csbeq1a 3007	. . . . . . . . 9 |- ( x = w -> A = [_ w / x ]_ A )
15	14	eqeq2d 2149	. . . . . . . 8 |- ( x = w -> ( y = A <-> y = [_ w / x ]_ A ) )
16	11, 13, 15	spcgf 2763	. . . . . . 7 |- ( w e. _V -> ( A. x y = A -> y = [_ w / x ]_ A ) )
17	10, 16	ax-mp 5	. . . . . 6 |- ( A. x y = A -> y = [_ w / x ]_ A )
18	9, 17	eqtr3d 2172	. . . . 5 |- ( A. x y = A -> [_ z / x ]_ A = [_ w / x ]_ A )
19	18	alrimivv 1847	. . . 4 |- ( A. x y = A -> A. z A. w [_ z / x ]_ A = [_ w / x ]_ A )
20		sbnfc2 3055	. . . 4 |- ( F/_ x A <-> A. z A. w [_ z / x ]_ A = [_ w / x ]_ A )
21	19, 20	sylibr 133	. . 3 |- ( A. x y = A -> F/_ x A )
22	21	exlimiv 1577	. 2 |- ( E. y A. x y = A -> F/_ x A )
23	1, 22	syl 14	1 |- ( E! y A. x y = A -> F/_ x A )

Syntax hints:   -> wi 4   A.wal 1329   = wceq 1331   E.wex 1468   e. wcel 1480   E!weu 1997   F/_wnfc 2266   _Vcvv 2681   [_csb 2998

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-io 698  ax-5 1423  ax-7 1424  ax-gen 1425  ax-ie1 1469  ax-ie2 1470  ax-8 1482  ax-10 1483  ax-11 1484  ax-i12 1485  ax-bndl 1486  ax-4 1487  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515  ax-ext 2119

This theorem depends on definitions:  df-bi 116  df-tru 1334  df-nf 1437  df-sb 1736  df-eu 2000  df-clab 2124  df-cleq 2130  df-clel 2133  df-nfc 2268  df-v 2683  df-sbc 2905  df-csb 2999

This theorem is referenced by:  eusvnfb  4370  eusv2i  4371