Theorem elsb3 1949

Description: Substitution applied to an atomic membership wff. (Contributed by NM, 7-Nov-2006.) (Proof shortened by Andrew Salmon, 14-Jun-2011.)

Assertion

Ref	Expression
elsb3	|- ( [ y / x ] x e. z <-> y e. z )

Distinct variable group:   x, z

Proof of Theorem elsb3

Dummy variable w is distinct from all other variables.

Step	Hyp	Ref	Expression
1		ax-17 1506	. . . . 5 |- ( x e. z -> A. w x e. z )
2		elequ1 1690	. . . . 5 |- ( w = x -> ( w e. z <-> x e. z ) )
3	1, 2	sbieh 1763	. . . 4 |- ( [ x / w ] w e. z <-> x e. z )
4	3	sbbii 1738	. . 3 |- ( [ y / x ] [ x / w ] w e. z <-> [ y / x ] x e. z )
5		ax-17 1506	. . . 4 |- ( w e. z -> A. x w e. z )
6	5	sbco2h 1935	. . 3 |- ( [ y / x ] [ x / w ] w e. z <-> [ y / w ] w e. z )
7	4, 6	bitr3i 185	. 2 |- ( [ y / x ] x e. z <-> [ y / w ] w e. z )
8		equsb1 1758	. . . 4 |- [ y / w ] w = y
9		elequ1 1690	. . . . 5 |- ( w = y -> ( w e. z <-> y e. z ) )
10	9	sbimi 1737	. . . 4 |- ( [ y / w ] w = y -> [ y / w ] ( w e. z <-> y e. z ) )
11	8, 10	ax-mp 5	. . 3 |- [ y / w ] ( w e. z <-> y e. z )
12		sbbi 1930	. . 3 |- ( [ y / w ] ( w e. z <-> y e. z ) <-> ( [ y / w ] w e. z <-> [ y / w ] y e. z ) )
13	11, 12	mpbi 144	. 2 |- ( [ y / w ] w e. z <-> [ y / w ] y e. z )
14		ax-17 1506	. . 3 |- ( y e. z -> A. w y e. z )
15	14	sbh 1749	. 2 |- ( [ y / w ] y e. z <-> y e. z )
16	7, 13, 15	3bitri 205	1 |- ( [ y / x ] x e. z <-> y e. z )

Syntax hints:   <-> wb 104   [wsb 1735

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-13 1491  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515

This theorem depends on definitions:  df-bi 116  df-nf 1437  df-sb 1736

This theorem is referenced by:  cvjust  2132