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Theorem nfbii2 33634
Description: Equality deduction for not-freeness. (Contributed by Giovanni Mascellani, 10-Apr-2018.)
Assertion
Ref Expression
nfbii2 (∀𝑥(𝜑𝜓) → (Ⅎ𝑥𝜑 ↔ Ⅎ𝑥𝜓))

Proof of Theorem nfbii2
StepHypRef Expression
1 nfa1 2025 . 2 𝑥𝑥(𝜑𝜓)
2 sp 2051 . 2 (∀𝑥(𝜑𝜓) → (𝜑𝜓))
31, 2nfbidf 2090 1 (∀𝑥(𝜑𝜓) → (Ⅎ𝑥𝜑 ↔ Ⅎ𝑥𝜓))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 196  wal 1478  wnf 1705
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1719  ax-4 1734  ax-5 1836  ax-6 1885  ax-7 1932  ax-10 2016  ax-12 2044
This theorem depends on definitions:  df-bi 197  df-or 385  df-ex 1702  df-nf 1707
This theorem is referenced by: (None)
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