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Mirrors > Home > MPE Home > Th. List > dffun7 | Structured version Visualization version GIF version |
Description: Alternate definition of a function. One possibility for the definition of a function in [Enderton] p. 42. (Enderton's definition is ambiguous because "there is only one" could mean either "there is at most one" or "there is exactly one." However, dffun8 6058 shows that it doesn't matter which meaning we pick.) (Contributed by NM, 4-Nov-2002.) |
Ref | Expression |
---|---|
dffun7 | ⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥 ∈ dom 𝐴∃*𝑦 𝑥𝐴𝑦)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | dffun6 6045 | . 2 ⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥∃*𝑦 𝑥𝐴𝑦)) | |
2 | moabs 2648 | . . . . . 6 ⊢ (∃*𝑦 𝑥𝐴𝑦 ↔ (∃𝑦 𝑥𝐴𝑦 → ∃*𝑦 𝑥𝐴𝑦)) | |
3 | vex 3351 | . . . . . . . 8 ⊢ 𝑥 ∈ V | |
4 | 3 | eldm 5458 | . . . . . . 7 ⊢ (𝑥 ∈ dom 𝐴 ↔ ∃𝑦 𝑥𝐴𝑦) |
5 | 4 | imbi1i 338 | . . . . . 6 ⊢ ((𝑥 ∈ dom 𝐴 → ∃*𝑦 𝑥𝐴𝑦) ↔ (∃𝑦 𝑥𝐴𝑦 → ∃*𝑦 𝑥𝐴𝑦)) |
6 | 2, 5 | bitr4i 267 | . . . . 5 ⊢ (∃*𝑦 𝑥𝐴𝑦 ↔ (𝑥 ∈ dom 𝐴 → ∃*𝑦 𝑥𝐴𝑦)) |
7 | 6 | albii 1893 | . . . 4 ⊢ (∀𝑥∃*𝑦 𝑥𝐴𝑦 ↔ ∀𝑥(𝑥 ∈ dom 𝐴 → ∃*𝑦 𝑥𝐴𝑦)) |
8 | df-ral 3064 | . . . 4 ⊢ (∀𝑥 ∈ dom 𝐴∃*𝑦 𝑥𝐴𝑦 ↔ ∀𝑥(𝑥 ∈ dom 𝐴 → ∃*𝑦 𝑥𝐴𝑦)) | |
9 | 7, 8 | bitr4i 267 | . . 3 ⊢ (∀𝑥∃*𝑦 𝑥𝐴𝑦 ↔ ∀𝑥 ∈ dom 𝐴∃*𝑦 𝑥𝐴𝑦) |
10 | 9 | anbi2i 729 | . 2 ⊢ ((Rel 𝐴 ∧ ∀𝑥∃*𝑦 𝑥𝐴𝑦) ↔ (Rel 𝐴 ∧ ∀𝑥 ∈ dom 𝐴∃*𝑦 𝑥𝐴𝑦)) |
11 | 1, 10 | bitri 264 | 1 ⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥 ∈ dom 𝐴∃*𝑦 𝑥𝐴𝑦)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 196 ∧ wa 383 ∀wal 1627 ∃wex 1850 ∈ wcel 2143 ∃*wmo 2617 ∀wral 3059 class class class wbr 4783 dom cdm 5248 Rel wrel 5253 Fun wfun 6024 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1868 ax-4 1883 ax-5 1989 ax-6 2055 ax-7 2091 ax-9 2152 ax-10 2172 ax-11 2188 ax-12 2201 ax-13 2406 ax-ext 2749 ax-sep 4911 ax-nul 4919 ax-pr 5033 |
This theorem depends on definitions: df-bi 197 df-or 384 df-an 385 df-3an 1071 df-tru 1632 df-ex 1851 df-nf 1856 df-sb 2048 df-eu 2620 df-mo 2621 df-clab 2756 df-cleq 2762 df-clel 2765 df-nfc 2900 df-ral 3064 df-rab 3068 df-v 3350 df-dif 3723 df-un 3725 df-in 3727 df-ss 3734 df-nul 4061 df-if 4223 df-sn 4314 df-pr 4316 df-op 4320 df-br 4784 df-opab 4844 df-id 5156 df-cnv 5256 df-co 5257 df-dm 5258 df-fun 6032 |
This theorem is referenced by: dffun8 6058 dffun9 6059 brdom5 9551 imasaddfnlem 16402 imasvscafn 16411 funressnfv 41729 |
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