Theorem cbvrexsv 2589

Description: Change bound variable by using a substitution. (Contributed by NM, 2-Mar-2008.) (Revised by Andrew Salmon, 11-Jul-2011.)

Assertion

Ref	Expression
cbvrexsv	|- ( E. x e. A ph <-> E. y e. A [ y / x ] ph )

Distinct variable groups:   x, A   ph, y   y, A

Allowed substitution hint:   ph( x)

Proof of Theorem cbvrexsv

Dummy variable z is distinct from all other variables.

Step	Hyp	Ref	Expression
1		nfv 1461	. . 3 |- F/ z ph
2		nfs1v 1856	. . 3 |- F/ x [ z / x ] ph
3		sbequ12 1694	. . 3 |- ( x = z -> ( ph <-> [ z / x ] ph ) )
4	1, 2, 3	cbvrex 2574	. 2 |- ( E. x e. A ph <-> E. z e. A [ z / x ] ph )
5		nfv 1461	. . . 4 |- F/ y ph
6	5	nfsb 1863	. . 3 |- F/ y [ z / x ] ph
7		nfv 1461	. . 3 |- F/ z [ y / x ] ph
8		sbequ 1761	. . 3 |- ( z = y -> ( [ z / x ] ph <-> [ y / x ] ph ) )
9	6, 7, 8	cbvrex 2574	. 2 |- ( E. z e. A [ z / x ] ph <-> E. y e. A [ y / x ] ph )
10	4, 9	bitri 182	1 |- ( E. x e. A ph <-> E. y e. A [ y / x ] ph )

Syntax hints:   <-> wb 103   [wsb 1685   E.wrex 2349

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-io 662  ax-5 1376  ax-7 1377  ax-gen 1378  ax-ie1 1422  ax-ie2 1423  ax-8 1435  ax-10 1436  ax-11 1437  ax-i12 1438  ax-bndl 1439  ax-4 1440  ax-17 1459  ax-i9 1463  ax-ial 1467  ax-i5r 1468  ax-ext 2063

This theorem depends on definitions:  df-bi 115  df-nf 1390  df-sb 1686  df-cleq 2074  df-clel 2077  df-nfc 2208  df-rex 2354

This theorem is referenced by:  rspesbca  2898  rexxpf  4501