Theorem cbvalh 1683

Description: Rule used to change bound variables, using implicit substitition. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 25-May-2011.)

Hypotheses

Ref	Expression
cbvalh.1	|- ( ph -> A. y ph )
cbvalh.2	|- ( ps -> A. x ps )
cbvalh.3	|- ( x = y -> ( ph <-> ps ) )

Assertion

Ref	Expression
cbvalh	|- ( A. x ph <-> A. y ps )

Proof of Theorem cbvalh

Step	Hyp	Ref	Expression
1		cbvalh.1	. . 3 |- ( ph -> A. y ph )
2		cbvalh.2	. . 3 |- ( ps -> A. x ps )
3		cbvalh.3	. . . 4 |- ( x = y -> ( ph <-> ps ) )
4	3	biimpd 142	. . 3 |- ( x = y -> ( ph -> ps ) )
5	1, 2, 4	cbv3h 1678	. 2 |- ( A. x ph -> A. y ps )
6	3	equcoms 1641	. . . 4 |- ( y = x -> ( ph <-> ps ) )
7	6	biimprd 156	. . 3 |- ( y = x -> ( ps -> ph ) )
8	2, 1, 7	cbv3h 1678	. 2 |- ( A. y ps -> A. x ph )
9	5, 8	impbii 124	1 |- ( A. x ph <-> A. y ps )

Syntax hints:   -> wi 4   <-> wb 103   A.wal 1287

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-5 1381  ax-7 1382  ax-gen 1383  ax-ie1 1427  ax-ie2 1428  ax-8 1440  ax-4 1445  ax-17 1464  ax-i9 1468  ax-ial 1472

This theorem depends on definitions:  df-bi 115  df-nf 1395

This theorem is referenced by:  cbval  1684  sb8h  1782  cbvalv  1842  sb9v  1902  sb8euh  1971