Theorem sbequ 1851

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 1850	. 2 |- ( x = y -> ( [ x / z ] ph -> [ y / z ] ph ) )
2		sbequi 1850	. . 3 |- ( y = x -> ( [ y / z ] ph -> [ x / z ] ph ) )
3	2	equcoms 1719	. 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 1773

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 1458  ax-7 1459  ax-gen 1460  ax-ie1 1504  ax-ie2 1505  ax-8 1515  ax-10 1516  ax-11 1517  ax-i12 1518  ax-4 1521  ax-17 1537  ax-i9 1541  ax-ial 1545  ax-i5r 1546

This theorem depends on definitions:  df-bi 117  df-nf 1472  df-sb 1774

This theorem is referenced by:  drsb2  1852  sbco2vlem  1960  sbco2v  1964  sbco2yz  1979  sbcocom  1986  sb10f  2011  hbsb4  2028  nfsb4or  2037  sb8eu  2055  sb8euh  2065  cbvab  2317  cbvralf  2718  cbvrexf  2719  cbvreu  2724  cbvralsv  2742  cbvrexsv  2743  cbvrab  2758  cbvreucsf  3145  cbvrabcsf  3146  sbss  3554  disjiun  4024  cbvopab1  4102  cbvmpt  4124  tfis  4615  findes  4635  cbviota  5220  sb8iota  5222  cbvriota  5884  uzind4s  9655  bezoutlemmain  12135  cbvrald  15280  setindft  15457