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Mirrors > Home > MPE Home > Th. List > Mathboxes > map0cor | Structured version Visualization version GIF version |
Description: A function exists iff an empty codomain is accompanied with an empty domain. (Contributed by Zhi Wang, 1-Oct-2024.) |
Ref | Expression |
---|---|
map0cor.1 | ⊢ (𝜑 → 𝐴 ∈ 𝑉) |
map0cor.2 | ⊢ (𝜑 → 𝐵 ∈ 𝑊) |
Ref | Expression |
---|---|
map0cor | ⊢ (𝜑 → ((𝐵 = ∅ → 𝐴 = ∅) ↔ ∃𝑓 𝑓:𝐴⟶𝐵)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | map0cor.2 | . 2 ⊢ (𝜑 → 𝐵 ∈ 𝑊) | |
2 | map0cor.1 | . 2 ⊢ (𝜑 → 𝐴 ∈ 𝑉) | |
3 | biid 260 | . . . . . . 7 ⊢ (𝐴 ≠ ∅ ↔ 𝐴 ≠ ∅) | |
4 | 3 | necon2bbii 2990 | . . . . . 6 ⊢ (𝐴 = ∅ ↔ ¬ 𝐴 ≠ ∅) |
5 | 4 | imbi2i 335 | . . . . 5 ⊢ ((𝐵 = ∅ → 𝐴 = ∅) ↔ (𝐵 = ∅ → ¬ 𝐴 ≠ ∅)) |
6 | imnan 399 | . . . . 5 ⊢ ((𝐵 = ∅ → ¬ 𝐴 ≠ ∅) ↔ ¬ (𝐵 = ∅ ∧ 𝐴 ≠ ∅)) | |
7 | 5, 6 | bitri 274 | . . . 4 ⊢ ((𝐵 = ∅ → 𝐴 = ∅) ↔ ¬ (𝐵 = ∅ ∧ 𝐴 ≠ ∅)) |
8 | map0g 8692 | . . . . 5 ⊢ ((𝐵 ∈ 𝑊 ∧ 𝐴 ∈ 𝑉) → ((𝐵 ↑m 𝐴) = ∅ ↔ (𝐵 = ∅ ∧ 𝐴 ≠ ∅))) | |
9 | 8 | notbid 317 | . . . 4 ⊢ ((𝐵 ∈ 𝑊 ∧ 𝐴 ∈ 𝑉) → (¬ (𝐵 ↑m 𝐴) = ∅ ↔ ¬ (𝐵 = ∅ ∧ 𝐴 ≠ ∅))) |
10 | 7, 9 | bitr4id 289 | . . 3 ⊢ ((𝐵 ∈ 𝑊 ∧ 𝐴 ∈ 𝑉) → ((𝐵 = ∅ → 𝐴 = ∅) ↔ ¬ (𝐵 ↑m 𝐴) = ∅)) |
11 | neq0 4282 | . . . 4 ⊢ (¬ (𝐵 ↑m 𝐴) = ∅ ↔ ∃𝑓 𝑓 ∈ (𝐵 ↑m 𝐴)) | |
12 | 11 | a1i 11 | . . 3 ⊢ ((𝐵 ∈ 𝑊 ∧ 𝐴 ∈ 𝑉) → (¬ (𝐵 ↑m 𝐴) = ∅ ↔ ∃𝑓 𝑓 ∈ (𝐵 ↑m 𝐴))) |
13 | elmapg 8648 | . . . 4 ⊢ ((𝐵 ∈ 𝑊 ∧ 𝐴 ∈ 𝑉) → (𝑓 ∈ (𝐵 ↑m 𝐴) ↔ 𝑓:𝐴⟶𝐵)) | |
14 | 13 | exbidv 1920 | . . 3 ⊢ ((𝐵 ∈ 𝑊 ∧ 𝐴 ∈ 𝑉) → (∃𝑓 𝑓 ∈ (𝐵 ↑m 𝐴) ↔ ∃𝑓 𝑓:𝐴⟶𝐵)) |
15 | 10, 12, 14 | 3bitrd 304 | . 2 ⊢ ((𝐵 ∈ 𝑊 ∧ 𝐴 ∈ 𝑉) → ((𝐵 = ∅ → 𝐴 = ∅) ↔ ∃𝑓 𝑓:𝐴⟶𝐵)) |
16 | 1, 2, 15 | syl2anc 583 | 1 ⊢ (𝜑 → ((𝐵 = ∅ → 𝐴 = ∅) ↔ ∃𝑓 𝑓:𝐴⟶𝐵)) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ↔ wb 205 ∧ wa 395 = wceq 1537 ∃wex 1777 ∈ wcel 2101 ≠ wne 2938 ∅c0 4259 ⟶wf 6443 (class class class)co 7295 ↑m cmap 8635 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1793 ax-4 1807 ax-5 1909 ax-6 1967 ax-7 2007 ax-8 2103 ax-9 2111 ax-10 2132 ax-11 2149 ax-12 2166 ax-ext 2704 ax-sep 5226 ax-nul 5233 ax-pow 5291 ax-pr 5355 ax-un 7608 |
This theorem depends on definitions: df-bi 206 df-an 396 df-or 844 df-3an 1087 df-tru 1540 df-fal 1550 df-ex 1778 df-nf 1782 df-sb 2063 df-mo 2535 df-eu 2564 df-clab 2711 df-cleq 2725 df-clel 2811 df-nfc 2884 df-ne 2939 df-ral 3060 df-rex 3069 df-rab 3224 df-v 3436 df-sbc 3719 df-csb 3835 df-dif 3892 df-un 3894 df-in 3896 df-ss 3906 df-nul 4260 df-if 4463 df-pw 4538 df-sn 4565 df-pr 4567 df-op 4571 df-uni 4842 df-iun 4929 df-br 5078 df-opab 5140 df-mpt 5161 df-id 5491 df-xp 5597 df-rel 5598 df-cnv 5599 df-co 5600 df-dm 5601 df-rn 5602 df-res 5603 df-ima 5604 df-iota 6399 df-fun 6449 df-fn 6450 df-f 6451 df-fv 6455 df-ov 7298 df-oprab 7299 df-mpo 7300 df-1st 7851 df-2nd 7852 df-map 8637 |
This theorem is referenced by: (None) |
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