Theorem sb8h 1848

Description: Substitution of variable in universal quantifier. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 25-May-2011.) (Proof shortened by Jim Kingdon, 15-Jan-2018.)

Hypothesis

Ref	Expression
sb8h.1	|- ( ph -> A. y ph )

Assertion

Ref	Expression
sb8h	|- ( A. x ph <-> A. y [ y / x ] ph )

Proof of Theorem sb8h

Step	Hyp	Ref	Expression
1		sb8h.1	. 2 |- ( ph -> A. y ph )
2	1	hbsb3 1802	. 2 |- ( [ y / x ] ph -> A. x [ y / x ] ph )
3		sbequ12 1765	. 2 |- ( x = y -> ( ph <-> [ y / x ] ph ) )
4	1, 2, 3	cbvalh 1747	1 |- ( A. x ph <-> A. y [ y / x ] ph )

Syntax hints:   -> wi 4   <-> wb 104   A.wal 1347   [wsb 1756

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-5 1441  ax-7 1442  ax-gen 1443  ax-ie1 1487  ax-ie2 1488  ax-8 1498  ax-11 1500  ax-4 1504  ax-17 1520  ax-i9 1524  ax-ial 1528

This theorem depends on definitions:  df-bi 116  df-nf 1455  df-sb 1757

This theorem is referenced by:  sbhb  1934  sb8euh  2043