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Theorem mobidv 1978
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 1462 . 2 𝑥𝜑
2 mobidv.1 . 2 (𝜑 → (𝜓𝜒))
31, 2mobid 1977 1 (𝜑 → (∃*𝑥𝜓 ↔ ∃*𝑥𝜒))
Colors of variables: wff set class
Syntax hints:  wi 4  wb 103  ∃*wmo 1943
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-5 1377  ax-gen 1379  ax-ie1 1423  ax-ie2 1424  ax-4 1441  ax-17 1460  ax-ial 1468
This theorem depends on definitions:  df-bi 115  df-nf 1391  df-eu 1945  df-mo 1946
This theorem is referenced by:  mobii  1979  mosubopt  4431  dffun6f  4945  funmo  4947  1stconst  5873  2ndconst  5874
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