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Theorem sylnbi 613
Description: A mixed syllogism inference from a biconditional and an implication. Useful for substituting an antecedent with a definition. (Contributed by Wolf Lammen, 16-Dec-2013.)
Hypotheses
Ref Expression
sylnbi.1 (𝜑𝜓)
sylnbi.2 𝜓𝜒)
Assertion
Ref Expression
sylnbi 𝜑𝜒)

Proof of Theorem sylnbi
StepHypRef Expression
1 sylnbi.1 . . 3 (𝜑𝜓)
21notbii 604 . 2 𝜑 ↔ ¬ 𝜓)
3 sylnbi.2 . 2 𝜓𝜒)
42, 3sylbi 118 1 𝜑𝜒)
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4  wb 102
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105  ax-in1 554  ax-in2 555
This theorem depends on definitions:  df-bi 114
This theorem is referenced by:  sylnbir  614  mo2n  1944  reuun2  3248  regexmidlem1  4286  iotanul  4910  riotaund  5530  snnen2og  6353
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