NFE Home New Foundations Explorer < Previous   Next >
Nearby theorems
Mirrors  >  Home  >  NFE Home  >  Th. List  >  19.12 Unicode version

Theorem 19.12 1847
Description: Theorem 19.12 of [Margaris] p. 89. Assuming the converse is a mistake sometimes made by beginners! But sometimes the converse does hold, as in 19.12vv 1898 and r19.12sn 3789. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 3-Jan-2018.)
Assertion
Ref Expression
19.12

Proof of Theorem 19.12
StepHypRef Expression
1 nfa1 1788 . . 3  F/
21nfex 1843 . 2  F/
3 sp 1747 . . 3
43eximi 1576 . 2
52, 4alrimi 1765 1
Colors of variables: wff setvar class
Syntax hints:   wi 4  wal 1540  wex 1541
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
This theorem depends on definitions:  df-bi 177  df-ex 1542  df-nf 1545
This theorem is referenced by:  ax12olem2  1928
  Copyright terms: Public domain W3C validator