Theorem sbf 1751

Description: Substitution for a variable not free in a wff does not affect it. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 4-Oct-2016.)

Hypothesis

Ref	Expression
sbf.1	|- F/ x ph

Assertion

Ref	Expression
sbf	|- ( [ y / x ] ph <-> ph )

Proof of Theorem sbf

Step	Hyp	Ref	Expression
1		sbf.1	. . 3 |- F/ x ph
2	1	nfri 1500	. 2 |- ( ph -> A. x ph )
3	2	sbh 1750	1 |- ( [ y / x ] ph <-> ph )

Syntax hints:   <-> wb 104   F/wnf 1437   [wsb 1736

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-5 1424  ax-gen 1426  ax-ie1 1470  ax-ie2 1471  ax-4 1488  ax-i9 1511  ax-ial 1515

This theorem depends on definitions:  df-bi 116  df-nf 1438  df-sb 1737

This theorem is referenced by:  sbf2  1752  sbequ5  1756  sbequ6  1757  sbt  1758  sblim  1931  moimv  2066  moanim  2074  sbabel  2308  nfcdeq  2910  oprcl  3737