Theorem sbequ 1854

Description: An equality theorem for substitution. Used in proof of Theorem 9.7 in [Megill] p. 449 (p. 16 of the preprint). (Contributed by NM, 5-Aug-1993.)

Assertion

Ref	Expression
sbequ	|- ( x = y -> ( [ x / z ] ph <-> [ y / z ] ph ) )

Proof of Theorem sbequ

Step	Hyp	Ref	Expression
1		sbequi 1853	. 2 |- ( x = y -> ( [ x / z ] ph -> [ y / z ] ph ) )
2		sbequi 1853	. . 3 |- ( y = x -> ( [ y / z ] ph -> [ x / z ] ph ) )
3	2	equcoms 1722	. 2 |- ( x = y -> ( [ y / z ] ph -> [ x / z ] ph ) )
4	1, 3	impbid 129	1 |- ( x = y -> ( [ x / z ] ph <-> [ y / z ] ph ) )

Syntax hints:   -> wi 4   <-> wb 105   [wsb 1776

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-io 710  ax-5 1461  ax-7 1462  ax-gen 1463  ax-ie1 1507  ax-ie2 1508  ax-8 1518  ax-10 1519  ax-11 1520  ax-i12 1521  ax-4 1524  ax-17 1540  ax-i9 1544  ax-ial 1548  ax-i5r 1549

This theorem depends on definitions:  df-bi 117  df-nf 1475  df-sb 1777

This theorem is referenced by:  drsb2  1855  sbco2vlem  1963  sbco2v  1967  sbco2yz  1982  sbcocom  1989  sb10f  2014  hbsb4  2031  nfsb4or  2040  sb8eu  2058  sb8euh  2068  cbvab  2320  cbvralf  2721  cbvrexf  2722  cbvreu  2727  cbvralsv  2745  cbvrexsv  2746  cbvrab  2761  cbvreucsf  3149  cbvrabcsf  3150  sbss  3558  disjiun  4028  cbvopab1  4106  cbvmpt  4128  tfis  4619  findes  4639  cbviota  5224  sb8iota  5226  cbvriota  5888  uzind4s  9664  bezoutlemmain  12165  cbvrald  15434  setindft  15611