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Mirrors > Home > ILE Home > Th. List > 0fv | GIF version |
Description: Function value of the empty set. (Contributed by Stefan O'Rear, 26-Nov-2014.) |
Ref | Expression |
---|---|
0fv | ⊢ (∅‘𝐴) = ∅ |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-fv 5126 | . 2 ⊢ (∅‘𝐴) = (℩𝑥𝐴∅𝑥) | |
2 | noel 3362 | . . . . . 6 ⊢ ¬ 〈𝐴, 𝑥〉 ∈ ∅ | |
3 | df-br 3925 | . . . . . 6 ⊢ (𝐴∅𝑥 ↔ 〈𝐴, 𝑥〉 ∈ ∅) | |
4 | 2, 3 | mtbir 660 | . . . . 5 ⊢ ¬ 𝐴∅𝑥 |
5 | 4 | nex 1476 | . . . 4 ⊢ ¬ ∃𝑥 𝐴∅𝑥 |
6 | euex 2027 | . . . 4 ⊢ (∃!𝑥 𝐴∅𝑥 → ∃𝑥 𝐴∅𝑥) | |
7 | 5, 6 | mto 651 | . . 3 ⊢ ¬ ∃!𝑥 𝐴∅𝑥 |
8 | iotanul 5098 | . . 3 ⊢ (¬ ∃!𝑥 𝐴∅𝑥 → (℩𝑥𝐴∅𝑥) = ∅) | |
9 | 7, 8 | ax-mp 5 | . 2 ⊢ (℩𝑥𝐴∅𝑥) = ∅ |
10 | 1, 9 | eqtri 2158 | 1 ⊢ (∅‘𝐴) = ∅ |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 = wceq 1331 ∃wex 1468 ∈ wcel 1480 ∃!weu 1997 ∅c0 3358 〈cop 3525 class class class wbr 3924 ℩cio 5081 ‘cfv 5118 |
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-in1 603 ax-in2 604 ax-io 698 ax-5 1423 ax-7 1424 ax-gen 1425 ax-ie1 1469 ax-ie2 1470 ax-8 1482 ax-10 1483 ax-11 1484 ax-i12 1485 ax-bndl 1486 ax-4 1487 ax-17 1506 ax-i9 1510 ax-ial 1514 ax-i5r 1515 ax-ext 2119 |
This theorem depends on definitions: df-bi 116 df-tru 1334 df-fal 1337 df-nf 1437 df-sb 1736 df-eu 2000 df-clab 2124 df-cleq 2130 df-clel 2133 df-nfc 2268 df-ral 2419 df-rex 2420 df-v 2683 df-dif 3068 df-in 3072 df-ss 3079 df-nul 3359 df-sn 3528 df-uni 3732 df-br 3925 df-iota 5083 df-fv 5126 |
This theorem is referenced by: strsl0 11996 |
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