Theorem sbhb 2438

Description: Two ways of expressing " x is (effectively) not free in ph." (Contributed by NM, 29-May-2009.)

Assertion

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

Distinct variable group:   ph, y

Allowed substitution hint:   ph( x)

Proof of Theorem sbhb

Step	Hyp	Ref	Expression
1		nfv 1843	. . . 4 |- F/ y ph
2	1	sb8 2424	. . 3 |- ( A. x ph <-> A. y [ y / x ] ph )
3	2	imbi2i 326	. 2 |- ( ( ph -> A. x ph ) <-> ( ph -> A. y [ y / x ] ph ) )
4		19.21v 1868	. 2 |- ( A. y ( ph -> [ y / x ] ph ) <-> ( ph -> A. y [ y / x ] ph ) )
5	3, 4	bitr4i 267	1 |- ( ( ph -> A. x ph ) <-> A. y ( ph -> [ y / x ] ph ) )

Syntax hints:   -> wi 4   <-> wb 196   A.wal 1481   [wsb 1880

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-ex 1705  df-nf 1710  df-sb 1881

This theorem is referenced by: (None)