Theorem sbequ 1828

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 1827	. 2 |- ( x = y -> ( [ x / z ] ph -> [ y / z ] ph ) )
2		sbequi 1827	. . 3 |- ( y = x -> ( [ y / z ] ph -> [ x / z ] ph ) )
3	2	equcoms 1696	. 2 |- ( x = y -> ( [ y / z ] ph -> [ x / z ] ph ) )
4	1, 3	impbid 128	1 |- ( x = y -> ( [ x / z ] ph <-> [ y / z ] ph ) )

Syntax hints:   -> wi 4   <-> wb 104   [wsb 1750

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 1435  ax-7 1436  ax-gen 1437  ax-ie1 1481  ax-ie2 1482  ax-8 1492  ax-10 1493  ax-11 1494  ax-i12 1495  ax-4 1498  ax-17 1514  ax-i9 1518  ax-ial 1522  ax-i5r 1523

This theorem depends on definitions:  df-bi 116  df-nf 1449  df-sb 1751

This theorem is referenced by:  drsb2  1829  sbco2vlem  1932  sbco2v  1936  sbco2yz  1951  sbcocom  1958  sb10f  1983  hbsb4  2000  nfsb4or  2009  sb8eu  2027  sb8euh  2037  cbvab  2290  cbvralf  2685  cbvrexf  2686  cbvreu  2690  cbvralsv  2708  cbvrexsv  2709  cbvrab  2724  cbvreucsf  3109  cbvrabcsf  3110  sbss  3517  disjiun  3977  cbvopab1  4055  cbvmpt  4077  tfis  4560  findes  4580  cbviota  5158  sb8iota  5160  cbvriota  5808  uzind4s  9528  bezoutlemmain  11931  cbvrald  13669  setindft  13847