Theorem sbequ1 1748

Description: An equality theorem for substitution. (Contributed by NM, 5-Aug-1993.)

Assertion

Ref	Expression
sbequ1	|- ( x = y -> ( ph -> [ y / x ] ph ) )

Proof of Theorem sbequ1

Step	Hyp	Ref	Expression
1		pm3.4 331	. . 3 |- ( ( x = y /\ ph ) -> ( x = y -> ph ) )
2		19.8a 1570	. . 3 |- ( ( x = y /\ ph ) -> E. x ( x = y /\ ph ) )
3		df-sb 1743	. . 3 |- ( [ y / x ] ph <-> ( ( x = y -> ph ) /\ E. x ( x = y /\ ph ) ) )
4	1, 2, 3	sylanbrc 414	. 2 |- ( ( x = y /\ ph ) -> [ y / x ] ph )
5	4	ex 114	1 |- ( x = y -> ( ph -> [ y / x ] ph ) )

Syntax hints:   -> wi 4   /\ wa 103   E.wex 1472   [wsb 1742

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-gen 1429  ax-ie1 1473  ax-ie2 1474  ax-4 1490

This theorem depends on definitions:  df-bi 116  df-sb 1743

This theorem is referenced by:  sbequ12  1751  sbequi  1819  sb6rf  1833  mo2n  2034  bj-bdfindes  13535  bj-findes  13567