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Theorem fnimaeq0 6474
Description: Images under a function never map nonempty sets to empty sets. EDITORIAL: usable in fnwe2lem2 39529. (Contributed by Stefan O'Rear, 21-Jan-2015.)
Assertion
Ref Expression
fnimaeq0 ((𝐹 Fn 𝐴𝐵𝐴) → ((𝐹𝐵) = ∅ ↔ 𝐵 = ∅))

Proof of Theorem fnimaeq0
StepHypRef Expression
1 imadisj 5941 . 2 ((𝐹𝐵) = ∅ ↔ (dom 𝐹𝐵) = ∅)
2 incom 4175 . . . 4 (dom 𝐹𝐵) = (𝐵 ∩ dom 𝐹)
3 fndm 6448 . . . . . . 7 (𝐹 Fn 𝐴 → dom 𝐹 = 𝐴)
43sseq2d 3996 . . . . . 6 (𝐹 Fn 𝐴 → (𝐵 ⊆ dom 𝐹𝐵𝐴))
54biimpar 478 . . . . 5 ((𝐹 Fn 𝐴𝐵𝐴) → 𝐵 ⊆ dom 𝐹)
6 df-ss 3949 . . . . 5 (𝐵 ⊆ dom 𝐹 ↔ (𝐵 ∩ dom 𝐹) = 𝐵)
75, 6sylib 219 . . . 4 ((𝐹 Fn 𝐴𝐵𝐴) → (𝐵 ∩ dom 𝐹) = 𝐵)
82, 7syl5eq 2865 . . 3 ((𝐹 Fn 𝐴𝐵𝐴) → (dom 𝐹𝐵) = 𝐵)
98eqeq1d 2820 . 2 ((𝐹 Fn 𝐴𝐵𝐴) → ((dom 𝐹𝐵) = ∅ ↔ 𝐵 = ∅))
101, 9syl5bb 284 1 ((𝐹 Fn 𝐴𝐵𝐴) → ((𝐹𝐵) = ∅ ↔ 𝐵 = ∅))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 207  wa 396   = wceq 1528  cin 3932  wss 3933  c0 4288  dom cdm 5548  cima 5551   Fn wfn 6343
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1787  ax-4 1801  ax-5 1902  ax-6 1961  ax-7 2006  ax-8 2107  ax-9 2115  ax-10 2136  ax-11 2151  ax-12 2167  ax-ext 2790  ax-sep 5194  ax-nul 5201  ax-pr 5320
This theorem depends on definitions:  df-bi 208  df-an 397  df-or 842  df-3an 1081  df-tru 1531  df-ex 1772  df-nf 1776  df-sb 2061  df-mo 2615  df-eu 2647  df-clab 2797  df-cleq 2811  df-clel 2890  df-nfc 2960  df-ral 3140  df-rex 3141  df-rab 3144  df-v 3494  df-dif 3936  df-un 3938  df-in 3940  df-ss 3949  df-nul 4289  df-if 4464  df-sn 4558  df-pr 4560  df-op 4564  df-br 5058  df-opab 5120  df-xp 5554  df-cnv 5556  df-dm 5558  df-rn 5559  df-res 5560  df-ima 5561  df-fn 6351
This theorem is referenced by:  ipodrsima  17763  mdegldg  24587  ig1peu  24692  ig1pdvds  24697  dimval  30900  dimvalfi  30901  kelac1  39541
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