Theorem elsb4 1926

Description: Substitution applied to an atomic membership wff. (Contributed by Rodolfo Medina, 3-Apr-2010.) (Proof shortened by Andrew Salmon, 14-Jun-2011.)

Assertion

Ref	Expression
elsb4	|- ( [ y / x ] z e. x <-> z e. y )

Distinct variable group:   x, z

Proof of Theorem elsb4

Dummy variable w is distinct from all other variables.

Step	Hyp	Ref	Expression
1		ax-17 1487	. . . . 5 |- ( z e. x -> A. w z e. x )
2		elequ2 1672	. . . . 5 |- ( w = x -> ( z e. w <-> z e. x ) )
3	1, 2	sbieh 1744	. . . 4 |- ( [ x / w ] z e. w <-> z e. x )
4	3	sbbii 1719	. . 3 |- ( [ y / x ] [ x / w ] z e. w <-> [ y / x ] z e. x )
5		ax-17 1487	. . . 4 |- ( z e. w -> A. x z e. w )
6	5	sbco2h 1911	. . 3 |- ( [ y / x ] [ x / w ] z e. w <-> [ y / w ] z e. w )
7	4, 6	bitr3i 185	. 2 |- ( [ y / x ] z e. x <-> [ y / w ] z e. w )
8		equsb1 1739	. . . 4 |- [ y / w ] w = y
9		elequ2 1672	. . . . 5 |- ( w = y -> ( z e. w <-> z e. y ) )
10	9	sbimi 1718	. . . 4 |- ( [ y / w ] w = y -> [ y / w ] ( z e. w <-> z e. y ) )
11	8, 10	ax-mp 7	. . 3 |- [ y / w ] ( z e. w <-> z e. y )
12		sbbi 1906	. . 3 |- ( [ y / w ] ( z e. w <-> z e. y ) <-> ( [ y / w ] z e. w <-> [ y / w ] z e. y ) )
13	11, 12	mpbi 144	. 2 |- ( [ y / w ] z e. w <-> [ y / w ] z e. y )
14		ax-17 1487	. . 3 |- ( z e. y -> A. w z e. y )
15	14	sbh 1730	. 2 |- ( [ y / w ] z e. y <-> z e. y )
16	7, 13, 15	3bitri 205	1 |- ( [ y / x ] z e. x <-> z e. y )

Syntax hints:   <-> wb 104   [wsb 1716

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 681  ax-5 1404  ax-7 1405  ax-gen 1406  ax-ie1 1450  ax-ie2 1451  ax-8 1463  ax-10 1464  ax-11 1465  ax-i12 1466  ax-bndl 1467  ax-4 1468  ax-14 1473  ax-17 1487  ax-i9 1491  ax-ial 1495  ax-i5r 1496

This theorem depends on definitions:  df-bi 116  df-nf 1418  df-sb 1717

This theorem is referenced by: (None)