Theorem equsalv 1793

Description: An equivalence related to implicit substitution. Version of equsal 1727 with a disjoint variable condition. (Contributed by NM, 2-Jun-1993.) (Revised by BJ, 31-May-2019.)

Hypotheses

Ref	Expression
equsalv.nf	|- F/ x ps
equsalv.1	|- ( x = y -> ( ph <-> ps ) )

Assertion

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

Distinct variable group:   x, y

Allowed substitution hints:   ph( x, y)   ps( x, y)

Proof of Theorem equsalv

Step	Hyp	Ref	Expression
1		equsalv.nf	. . 3 |- F/ x ps
2	1	19.23 1678	. 2 |- ( A. x ( x = y -> ps ) <-> ( E. x x = y -> ps ) )
3		equsalv.1	. . . 4 |- ( x = y -> ( ph <-> ps ) )
4	3	pm5.74i 180	. . 3 |- ( ( x = y -> ph ) <-> ( x = y -> ps ) )
5	4	albii 1470	. 2 |- ( A. x ( x = y -> ph ) <-> A. x ( x = y -> ps ) )
6		a9ev 1697	. . 3 |- E. x x = y
7	6	a1bi 243	. 2 |- ( ps <-> ( E. x x = y -> ps ) )
8	2, 5, 7	3bitr4i 212	1 |- ( A. x ( x = y -> ph ) <-> ps )

Syntax hints:   -> wi 4   <-> wb 105   A.wal 1351   F/wnf 1460   E.wex 1492

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-5 1447  ax-gen 1449  ax-ie1 1493  ax-ie2 1494  ax-4 1510  ax-i9 1530  ax-ial 1534  ax-i5r 1535

This theorem depends on definitions:  df-bi 117  df-nf 1461

This theorem is referenced by:  nfabdw  2338