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Mirrors > Home > MPE Home > Th. List > nf5-1 | Structured version Visualization version GIF version |
Description: One direction of nf5 2272 can be proved with a smaller footprint on axiom usage. (Contributed by Wolf Lammen, 16-Sep-2021.) |
Ref | Expression |
---|---|
nf5-1 | ⊢ (∀𝑥(𝜑 → ∀𝑥𝜑) → Ⅎ𝑥𝜑) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | exim 1829 | . . 3 ⊢ (∀𝑥(𝜑 → ∀𝑥𝜑) → (∃𝑥𝜑 → ∃𝑥∀𝑥𝜑)) | |
2 | hbe1a 2133 | . . 3 ⊢ (∃𝑥∀𝑥𝜑 → ∀𝑥𝜑) | |
3 | 1, 2 | syl6 35 | . 2 ⊢ (∀𝑥(𝜑 → ∀𝑥𝜑) → (∃𝑥𝜑 → ∀𝑥𝜑)) |
4 | 3 | nfd 1785 | 1 ⊢ (∀𝑥(𝜑 → ∀𝑥𝜑) → Ⅎ𝑥𝜑) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∀wal 1532 ∃wex 1774 Ⅎwnf 1778 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1790 ax-4 1804 ax-10 2130 |
This theorem depends on definitions: df-bi 206 df-ex 1775 df-nf 1779 |
This theorem is referenced by: nf5i 2135 nf5dh 2136 nf5d 2274 hbnt 2284 19.9ht 2309 |
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