De Morgan's Laws (Logic)/Disjunction of Negations

Theorems

Formulation 1

$\neg p \lor \neg q \dashv \vdash \neg \paren {p \land q}$


Formulation 2

$\vdash \paren {\neg p \lor \neg q} \iff \paren {\neg \paren {p \land q} }$


Also see


Sources

  • 1971: Robert H. Kasriel: Undergraduate Topology ... (previous) ... (next): $\S 1.2$: Some Remarks on the Use of the Connectives and, or, implies: Exercise $4$
  • 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): De Morgan's laws
  • 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): De Morgan's laws
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