Mathbox for Peter Mazsa |
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Mirrors > Home > MPE Home > Th. List > Mathboxes > nexmo1 | Structured version Visualization version GIF version |
Description: If there is no case where wff is true, it is true for at most one case. (Contributed by Peter Mazsa, 27-Sep-2021.) |
Ref | Expression |
---|---|
nexmo1 | ⊢ (¬ ∃𝑥𝜑 → ∃*𝑥𝜑) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | pm2.21 123 | . 2 ⊢ (¬ ∃𝑥𝜑 → (∃𝑥𝜑 → ∃!𝑥𝜑)) | |
2 | moeu 2667 | . 2 ⊢ (∃*𝑥𝜑 ↔ (∃𝑥𝜑 → ∃!𝑥𝜑)) | |
3 | 1, 2 | sylibr 236 | 1 ⊢ (¬ ∃𝑥𝜑 → ∃*𝑥𝜑) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ∃wex 1779 ∃*wmo 2619 ∃!weu 2652 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1795 ax-4 1809 ax-5 1910 ax-6 1969 |
This theorem depends on definitions: df-bi 209 df-an 399 df-ex 1780 df-mo 2621 df-eu 2653 |
This theorem is referenced by: (None) |
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