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Theorem 19.21h 2107
 Description: Theorem 19.21 of [Margaris] p. 90. The hypothesis can be thought of as "𝑥 is not free in 𝜑." See also 19.21 2062 and 19.21v 1855. (Contributed by NM, 1-Aug-2017.) (Proof shortened by Wolf Lammen, 1-Jan-2018.)
Hypothesis
Ref Expression
19.21h.1 (𝜑 → ∀𝑥𝜑)
Assertion
Ref Expression
19.21h (∀𝑥(𝜑𝜓) ↔ (𝜑 → ∀𝑥𝜓))

Proof of Theorem 19.21h
StepHypRef Expression
1 19.21h.1 . . 3 (𝜑 → ∀𝑥𝜑)
21nf5i 2011 . 2 𝑥𝜑
3219.21 2062 1 (∀𝑥(𝜑𝜓) ↔ (𝜑 → ∀𝑥𝜓))
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ↔ wb 195  ∀wal 1473 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728  ax-5 1827  ax-6 1875  ax-7 1922  ax-10 2006  ax-12 2034 This theorem depends on definitions:  df-bi 196  df-ex 1696  df-nf 1701 This theorem is referenced by:  hbim1  2110
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