Theorem elsb1 2174

Description: Substitution for the first argument of the non-logical predicate in an atomic formula. See elsb2 2175 for substitution for the second argument. (Contributed by NM, 7-Nov-2006.) (Proof shortened by Andrew Salmon, 14-Jun-2011.)

Assertion

Ref	Expression
elsb1	|- ( [ y / x ] x e. z <-> y e. z )

Distinct variable group:   x, z

Proof of Theorem elsb1

Dummy variable w is distinct from all other variables.

Step	Hyp	Ref	Expression
1		ax-17 1540	. . . . 5 |- ( x e. z -> A. w x e. z )
2		elequ1 2171	. . . . 5 |- ( w = x -> ( w e. z <-> x e. z ) )
3	1, 2	sbieh 1804	. . . 4 |- ( [ x / w ] w e. z <-> x e. z )
4	3	sbbii 1779	. . 3 |- ( [ y / x ] [ x / w ] w e. z <-> [ y / x ] x e. z )
5		ax-17 1540	. . . 4 |- ( w e. z -> A. x w e. z )
6	5	sbco2h 1983	. . 3 |- ( [ y / x ] [ x / w ] w e. z <-> [ y / w ] w e. z )
7	4, 6	bitr3i 186	. 2 |- ( [ y / x ] x e. z <-> [ y / w ] w e. z )
8		equsb1 1799	. . . 4 |- [ y / w ] w = y
9		elequ1 2171	. . . . 5 |- ( w = y -> ( w e. z <-> y e. z ) )
10	9	sbimi 1778	. . . 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 1978	. . 3 |- ( [ y / w ] ( w e. z <-> y e. z ) <-> ( [ y / w ] w e. z <-> [ y / w ] y e. z ) )
13	11, 12	mpbi 145	. 2 |- ( [ y / w ] w e. z <-> [ y / w ] y e. z )
14		ax-17 1540	. . 3 |- ( y e. z -> A. w y e. z )
15	14	sbh 1790	. 2 |- ( [ y / w ] y e. z <-> y e. z )
16	7, 13, 15	3bitri 206	1 |- ( [ y / x ] x e. z <-> y e. z )

Syntax hints:   <-> wb 105   [wsb 1776

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 1461  ax-7 1462  ax-gen 1463  ax-ie1 1507  ax-ie2 1508  ax-8 1518  ax-10 1519  ax-11 1520  ax-i12 1521  ax-bndl 1523  ax-4 1524  ax-17 1540  ax-i9 1544  ax-ial 1548  ax-i5r 1549  ax-13 2169

This theorem depends on definitions:  df-bi 117  df-nf 1475  df-sb 1777

This theorem is referenced by:  cvjust  2191