Theorem cbvrexf 2708

Description: Rule used to change bound variables, using implicit substitution. (Contributed by FL, 27-Apr-2008.) (Revised by Mario Carneiro, 9-Oct-2016.) (Proof rewritten by Jim Kingdon, 10-Jun-2018.)

Hypotheses

Ref	Expression
cbvralf.1	|- F/_ x A
cbvralf.2	|- F/_ y A
cbvralf.3	|- F/ y ph
cbvralf.4	|- F/ x ps
cbvralf.5	|- ( x = y -> ( ph <-> ps ) )

Assertion

Ref	Expression
cbvrexf	|- ( E. x e. A ph <-> E. y e. A ps )

Proof of Theorem cbvrexf

Dummy variable z is distinct from all other variables.

Step	Hyp	Ref	Expression
1		nfv 1538	. . . 4 |- F/ z ( x e. A /\ ph )
2		cbvralf.1	. . . . . 6 |- F/_ x A
3	2	nfcri 2323	. . . . 5 |- F/ x z e. A
4		nfs1v 1949	. . . . 5 |- F/ x [ z / x ] ph
5	3, 4	nfan 1575	. . . 4 |- F/ x ( z e. A /\ [ z / x ] ph )
6		eleq1 2250	. . . . 5 |- ( x = z -> ( x e. A <-> z e. A ) )
7		sbequ12 1781	. . . . 5 |- ( x = z -> ( ph <-> [ z / x ] ph ) )
8	6, 7	anbi12d 473	. . . 4 |- ( x = z -> ( ( x e. A /\ ph ) <-> ( z e. A /\ [ z / x ] ph ) ) )
9	1, 5, 8	cbvex 1766	. . 3 |- ( E. x ( x e. A /\ ph ) <-> E. z ( z e. A /\ [ z / x ] ph ) )
10		cbvralf.2	. . . . . 6 |- F/_ y A
11	10	nfcri 2323	. . . . 5 |- F/ y z e. A
12		cbvralf.3	. . . . . 6 |- F/ y ph
13	12	nfsb 1956	. . . . 5 |- F/ y [ z / x ] ph
14	11, 13	nfan 1575	. . . 4 |- F/ y ( z e. A /\ [ z / x ] ph )
15		nfv 1538	. . . 4 |- F/ z ( y e. A /\ ps )
16		eleq1 2250	. . . . 5 |- ( z = y -> ( z e. A <-> y e. A ) )
17		sbequ 1850	. . . . . 6 |- ( z = y -> ( [ z / x ] ph <-> [ y / x ] ph ) )
18		cbvralf.4	. . . . . . 7 |- F/ x ps
19		cbvralf.5	. . . . . . 7 |- ( x = y -> ( ph <-> ps ) )
20	18, 19	sbie 1801	. . . . . 6 |- ( [ y / x ] ph <-> ps )
21	17, 20	bitrdi 196	. . . . 5 |- ( z = y -> ( [ z / x ] ph <-> ps ) )
22	16, 21	anbi12d 473	. . . 4 |- ( z = y -> ( ( z e. A /\ [ z / x ] ph ) <-> ( y e. A /\ ps ) ) )
23	14, 15, 22	cbvex 1766	. . 3 |- ( E. z ( z e. A /\ [ z / x ] ph ) <-> E. y ( y e. A /\ ps ) )
24	9, 23	bitri 184	. 2 |- ( E. x ( x e. A /\ ph ) <-> E. y ( y e. A /\ ps ) )
25		df-rex 2471	. 2 |- ( E. x e. A ph <-> E. x ( x e. A /\ ph ) )
26		df-rex 2471	. 2 |- ( E. y e. A ps <-> E. y ( y e. A /\ ps ) )
27	24, 25, 26	3bitr4i 212	1 |- ( E. x e. A ph <-> E. y e. A ps )

Syntax hints:   -> wi 4   /\ wa 104   <-> wb 105   F/wnf 1470   E.wex 1502   [wsb 1772   e. wcel 2158   F/_wnfc 2316   E.wrex 2466

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-io 710  ax-5 1457  ax-7 1458  ax-gen 1459  ax-ie1 1503  ax-ie2 1504  ax-8 1514  ax-10 1515  ax-11 1516  ax-i12 1517  ax-bndl 1519  ax-4 1520  ax-17 1536  ax-i9 1540  ax-ial 1544  ax-i5r 1545  ax-ext 2169

This theorem depends on definitions:  df-bi 117  df-nf 1471  df-sb 1773  df-cleq 2180  df-clel 2183  df-nfc 2318  df-rex 2471

This theorem is referenced by:  cbvrex  2712