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Theorem alexbii 1907
Description: Biconditional form of aleximi 1906. (Contributed by BJ, 16-Nov-2020.)
Hypothesis
Ref Expression
alexbii.1 (𝜑 → (𝜓𝜒))
Assertion
Ref Expression
alexbii (∀𝑥𝜑 → (∃𝑥𝜓 ↔ ∃𝑥𝜒))

Proof of Theorem alexbii
StepHypRef Expression
1 alexbii.1 . . . 4 (𝜑 → (𝜓𝜒))
21biimpd 219 . . 3 (𝜑 → (𝜓𝜒))
32aleximi 1906 . 2 (∀𝑥𝜑 → (∃𝑥𝜓 → ∃𝑥𝜒))
41biimprd 238 . . 3 (𝜑 → (𝜒𝜓))
54aleximi 1906 . 2 (∀𝑥𝜑 → (∃𝑥𝜒 → ∃𝑥𝜓))
63, 5impbid 202 1 (∀𝑥𝜑 → (∃𝑥𝜓 ↔ ∃𝑥𝜒))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 196  wal 1628  wex 1851
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1869  ax-4 1884
This theorem depends on definitions:  df-bi 197  df-ex 1852
This theorem is referenced by:  exbi  1922  exbidh  1944  exintrbi  1969  eleq2d  2835  bnj956  31179
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