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Theorem 19.9ht 1778
Description: A closed version of 19.9 1783. (Contributed by NM, 5-Aug-1993.)
Assertion
Ref Expression
19.9ht (x(φxφ) → (xφφ))

Proof of Theorem 19.9ht
StepHypRef Expression
1 df-ex 1542 . 2 (xφ ↔ ¬ x ¬ φ)
2 hbnt 1775 . . 3 (x(φxφ) → (¬ φx ¬ φ))
32con1d 116 . 2 (x(φxφ) → (¬ x ¬ φφ))
41, 3syl5bi 208 1 (x(φxφ) → (xφφ))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  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-11 1746
This theorem depends on definitions:  df-bi 177  df-ex 1542
This theorem is referenced by:  19.9t  1779  19.9hOLD  1781
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