NFE Home New Foundations Explorer < Previous   Next >
Nearby theorems
Mirrors  >  Home  >  NFE Home  >  Th. List  >  nfsb4 Unicode version

Theorem nfsb4 2081
Description: A variable not free remains so after substitution with a distinct variable. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 4-Oct-2016.)
Hypothesis
Ref Expression
nfsb4.1  F/
Assertion
Ref Expression
nfsb4  F/

Proof of Theorem nfsb4
StepHypRef Expression
1 nfsb4t 2080 . 2  F/  F/
2 nfsb4.1 . 2  F/
31, 2mpg 1548 1  F/
Colors of variables: wff setvar class
Syntax hints:   wn 3   wi 4  wal 1540   F/wnf 1544  wsb 1648
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925
This theorem depends on definitions:  df-bi 177  df-an 360  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649
This theorem is referenced by:  sbco2  2086  nfsb  2109  sbal1  2126
  Copyright terms: Public domain W3C validator