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Mirrors > Home > ILE Home > Th. List > eu5 | GIF version |
Description: Uniqueness in terms of "at most one." (Contributed by NM, 23-Mar-1995.) (Proof rewritten by Jim Kingdon, 27-May-2018.) |
Ref | Expression |
---|---|
eu5 | ⊢ (∃!𝑥𝜑 ↔ (∃𝑥𝜑 ∧ ∃*𝑥𝜑)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | euex 2043 | . . 3 ⊢ (∃!𝑥𝜑 → ∃𝑥𝜑) | |
2 | eumo 2045 | . . 3 ⊢ (∃!𝑥𝜑 → ∃*𝑥𝜑) | |
3 | 1, 2 | jca 304 | . 2 ⊢ (∃!𝑥𝜑 → (∃𝑥𝜑 ∧ ∃*𝑥𝜑)) |
4 | df-mo 2017 | . . . . 5 ⊢ (∃*𝑥𝜑 ↔ (∃𝑥𝜑 → ∃!𝑥𝜑)) | |
5 | 4 | biimpi 119 | . . . 4 ⊢ (∃*𝑥𝜑 → (∃𝑥𝜑 → ∃!𝑥𝜑)) |
6 | 5 | imp 123 | . . 3 ⊢ ((∃*𝑥𝜑 ∧ ∃𝑥𝜑) → ∃!𝑥𝜑) |
7 | 6 | ancoms 266 | . 2 ⊢ ((∃𝑥𝜑 ∧ ∃*𝑥𝜑) → ∃!𝑥𝜑) |
8 | 3, 7 | impbii 125 | 1 ⊢ (∃!𝑥𝜑 ↔ (∃𝑥𝜑 ∧ ∃*𝑥𝜑)) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 103 ↔ wb 104 ∃wex 1479 ∃!weu 2013 ∃*wmo 2014 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-io 699 ax-5 1434 ax-7 1435 ax-gen 1436 ax-ie1 1480 ax-ie2 1481 ax-8 1491 ax-10 1492 ax-11 1493 ax-i12 1494 ax-bndl 1496 ax-4 1497 ax-17 1513 ax-i9 1517 ax-ial 1521 ax-i5r 1522 |
This theorem depends on definitions: df-bi 116 df-nf 1448 df-sb 1750 df-eu 2016 df-mo 2017 |
This theorem is referenced by: exmoeu2 2061 euan 2069 eu4 2075 euim 2081 euexex 2098 2euex 2100 2euswapdc 2104 2exeu 2105 reu5 2676 reuss2 3397 funcnv3 5244 fnres 5298 fnopabg 5305 brprcneu 5473 dff3im 5624 recmulnqg 7323 uptx 12815 |
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