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Mirrors > Home > MPE Home > Th. List > abf | Structured version Visualization version GIF version |
Description: A class abstraction determined by a false formula is empty. (Contributed by NM, 20-Jan-2012.) Avoid ax-8 2108, ax-10 2137, ax-11 2154, ax-12 2171. (Revised by Gino Giotto, 30-Jun-2024.) |
Ref | Expression |
---|---|
abf.1 | ⊢ ¬ 𝜑 |
Ref | Expression |
---|---|
abf | ⊢ {𝑥 ∣ 𝜑} = ∅ |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | abf.1 | . . . 4 ⊢ ¬ 𝜑 | |
2 | 1 | bifal 1557 | . . 3 ⊢ (𝜑 ↔ ⊥) |
3 | 2 | abbii 2802 | . 2 ⊢ {𝑥 ∣ 𝜑} = {𝑥 ∣ ⊥} |
4 | dfnul4 4323 | . 2 ⊢ ∅ = {𝑥 ∣ ⊥} | |
5 | 3, 4 | eqtr4i 2763 | 1 ⊢ {𝑥 ∣ 𝜑} = ∅ |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 = wceq 1541 ⊥wfal 1553 {cab 2709 ∅c0 4321 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1797 ax-4 1811 ax-5 1913 ax-6 1971 ax-7 2011 ax-9 2116 ax-ext 2703 |
This theorem depends on definitions: df-bi 206 df-an 397 df-tru 1544 df-fal 1554 df-ex 1782 df-sb 2068 df-clab 2710 df-cleq 2724 df-dif 3950 df-nul 4322 |
This theorem is referenced by: csbprc 4405 mpo0 7490 fi0 9411 join0 18354 meet0 18355 addsrid 27437 muls01 27557 mulsrid 27558 fmla0disjsuc 34377 0qs 37227 pmapglb2xN 38631 |
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