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Mirrors > Home > MPE Home > Th. List > 2false | Structured version Visualization version GIF version |
Description: Two falsehoods are equivalent. (Contributed by NM, 4-Apr-2005.) (Proof shortened by Wolf Lammen, 19-May-2013.) |
Ref | Expression |
---|---|
2false.1 | ⊢ ¬ 𝜑 |
2false.2 | ⊢ ¬ 𝜓 |
Ref | Expression |
---|---|
2false | ⊢ (𝜑 ↔ 𝜓) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 2false.1 | . . 3 ⊢ ¬ 𝜑 | |
2 | 2false.2 | . . 3 ⊢ ¬ 𝜓 | |
3 | 1, 2 | 2th 253 | . 2 ⊢ (¬ 𝜑 ↔ ¬ 𝜓) |
4 | 3 | con4bii 310 | 1 ⊢ (𝜑 ↔ 𝜓) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 ↔ wb 195 |
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 196 |
This theorem is referenced by: bianfi 962 bifal 1488 iun0 4512 0iun 4513 0xp 5122 cnv0OLD 5455 co02 5566 0er 7667 0erOLD 7668 00lss 18763 00ply1bas 19431 2lgslem4 24931 signswch 29964 finxp0 32404 pexmidlem8N 34281 dandysum2p2e4 39814 |
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