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Mirrors > Home > MPE Home > Th. List > anor | Structured version Visualization version GIF version |
Description: Conjunction in terms of disjunction (De Morgan's law). Theorem *4.5 of [WhiteheadRussell] p. 120. (Contributed by NM, 3-Jan-1993.) (Proof shortened by Wolf Lammen, 3-Nov-2012.) |
Ref | Expression |
---|---|
anor | ⊢ ((𝜑 ∧ 𝜓) ↔ ¬ (¬ 𝜑 ∨ ¬ 𝜓)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | notnotb 315 | . 2 ⊢ ((𝜑 ∧ 𝜓) ↔ ¬ ¬ (𝜑 ∧ 𝜓)) | |
2 | ianor 979 | . 2 ⊢ (¬ (𝜑 ∧ 𝜓) ↔ (¬ 𝜑 ∨ ¬ 𝜓)) | |
3 | 1, 2 | xchbinx 334 | 1 ⊢ ((𝜑 ∧ 𝜓) ↔ ¬ (¬ 𝜑 ∨ ¬ 𝜓)) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 ↔ wb 205 ∧ wa 396 ∨ wo 844 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 |
This theorem depends on definitions: df-bi 206 df-an 397 df-or 845 |
This theorem is referenced by: pm3.1 989 pm3.11 990 dn1 1055 noran 1531 bropopvvv 7922 swrdnd0 14381 ifpananb 41104 iunrelexp0 41292 |
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