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Theorem mobidv 1936
 Description: Formula-building rule for "at most one" quantifier (deduction rule). (Contributed by Mario Carneiro, 7-Oct-2016.)
Hypothesis
Ref Expression
mobidv.1 (𝜑 → (𝜓𝜒))
Assertion
Ref Expression
mobidv (𝜑 → (∃*𝑥𝜓 ↔ ∃*𝑥𝜒))
Distinct variable group:   𝜑,𝑥
Allowed substitution hints:   𝜓(𝑥)   𝜒(𝑥)

Proof of Theorem mobidv
StepHypRef Expression
1 nfv 1421 . 2 𝑥𝜑
2 mobidv.1 . 2 (𝜑 → (𝜓𝜒))
31, 2mobid 1935 1 (𝜑 → (∃*𝑥𝜓 ↔ ∃*𝑥𝜒))
 Colors of variables: wff set class Syntax hints:   → wi 4   ↔ wb 98  ∃*wmo 1901 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-5 1336  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-4 1400  ax-17 1419  ax-ial 1427 This theorem depends on definitions:  df-bi 110  df-nf 1350  df-eu 1903  df-mo 1904 This theorem is referenced by:  mobii  1937  mosubopt  4405  dffun6f  4915  funmo  4917  1stconst  5842  2ndconst  5843
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