Theorem 2sb6rf 1977

Description: Reversed double substitution. (Contributed by NM, 3-Feb-2005.)

Hypotheses

Ref	Expression
2sb5rf.1	|- ( ph -> A. z ph )
2sb5rf.2	|- ( ph -> A. w ph )

Assertion

Ref	Expression
2sb6rf	|- ( ph <-> A. z A. w ( ( z = x /\ w = y ) -> [ z / x ] [ w / y ] ph ) )

Distinct variable groups:   x, y   x, w   y, z   z, w

Allowed substitution hints:   ph( x, y, z, w)

Proof of Theorem 2sb6rf

Step	Hyp	Ref	Expression
1		2sb5rf.1	. . 3 |- ( ph -> A. z ph )
2	1	sb6rf 1840	. 2 |- ( ph <-> A. z ( z = x -> [ z / x ] ph ) )
3		19.21v 1860	. . . 4 |- ( A. w ( z = x -> ( w = y -> [ w / y ] [ z / x ] ph ) ) <-> ( z = x -> A. w ( w = y -> [ w / y ] [ z / x ] ph ) ) )
4		sbcom2 1974	. . . . . . 7 |- ( [ z / x ] [ w / y ] ph <-> [ w / y ] [ z / x ] ph )
5	4	imbi2i 225	. . . . . 6 |- ( ( ( z = x /\ w = y ) -> [ z / x ] [ w / y ] ph ) <-> ( ( z = x /\ w = y ) -> [ w / y ] [ z / x ] ph ) )
6		impexp 261	. . . . . 6 |- ( ( ( z = x /\ w = y ) -> [ w / y ] [ z / x ] ph ) <-> ( z = x -> ( w = y -> [ w / y ] [ z / x ] ph ) ) )
7	5, 6	bitri 183	. . . . 5 |- ( ( ( z = x /\ w = y ) -> [ z / x ] [ w / y ] ph ) <-> ( z = x -> ( w = y -> [ w / y ] [ z / x ] ph ) ) )
8	7	albii 1457	. . . 4 |- ( A. w ( ( z = x /\ w = y ) -> [ z / x ] [ w / y ] ph ) <-> A. w ( z = x -> ( w = y -> [ w / y ] [ z / x ] ph ) ) )
9		2sb5rf.2	. . . . . . 7 |- ( ph -> A. w ph )
10	9	hbsbv 1928	. . . . . 6 |- ( [ z / x ] ph -> A. w [ z / x ] ph )
11	10	sb6rf 1840	. . . . 5 |- ( [ z / x ] ph <-> A. w ( w = y -> [ w / y ] [ z / x ] ph ) )
12	11	imbi2i 225	. . . 4 |- ( ( z = x -> [ z / x ] ph ) <-> ( z = x -> A. w ( w = y -> [ w / y ] [ z / x ] ph ) ) )
13	3, 8, 12	3bitr4ri 212	. . 3 |- ( ( z = x -> [ z / x ] ph ) <-> A. w ( ( z = x /\ w = y ) -> [ z / x ] [ w / y ] ph ) )
14	13	albii 1457	. 2 |- ( A. z ( z = x -> [ z / x ] ph ) <-> A. z A. w ( ( z = x /\ w = y ) -> [ z / x ] [ w / y ] ph ) )
15	2, 14	bitri 183	1 |- ( ph <-> A. z A. w ( ( z = x /\ w = y ) -> [ z / x ] [ w / y ] ph ) )

Syntax hints:   -> wi 4   /\ wa 103   <-> wb 104   A.wal 1340   [wsb 1749

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 699  ax-5 1434  ax-7 1435  ax-gen 1436  ax-ie1 1480  ax-ie2 1481  ax-8 1491  ax-10 1492  ax-11 1493  ax-i12 1494  ax-4 1497  ax-17 1513  ax-i9 1517  ax-ial 1521  ax-i5r 1522

This theorem depends on definitions:  df-bi 116  df-nf 1448  df-sb 1750

This theorem is referenced by: (None)