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Theorem tailini 35768
Description: A tail contains its initial element. (Contributed by Jeff Hankins, 25-Nov-2009.)
Hypothesis
Ref Expression
tailini.1 𝑋 = dom 𝐷
Assertion
Ref Expression
tailini ((𝐷 ∈ DirRel ∧ 𝐴 ∈ 𝑋) β†’ 𝐴 ∈ ((tailβ€˜π·)β€˜π΄))

Proof of Theorem tailini
StepHypRef Expression
1 tailini.1 . . 3 𝑋 = dom 𝐷
21dirref 18563 . 2 ((𝐷 ∈ DirRel ∧ 𝐴 ∈ 𝑋) β†’ 𝐴𝐷𝐴)
31eltail 35766 . . 3 ((𝐷 ∈ DirRel ∧ 𝐴 ∈ 𝑋 ∧ 𝐴 ∈ 𝑋) β†’ (𝐴 ∈ ((tailβ€˜π·)β€˜π΄) ↔ 𝐴𝐷𝐴))
433anidm23 1418 . 2 ((𝐷 ∈ DirRel ∧ 𝐴 ∈ 𝑋) β†’ (𝐴 ∈ ((tailβ€˜π·)β€˜π΄) ↔ 𝐴𝐷𝐴))
52, 4mpbird 257 1 ((𝐷 ∈ DirRel ∧ 𝐴 ∈ 𝑋) β†’ 𝐴 ∈ ((tailβ€˜π·)β€˜π΄))
Colors of variables: wff setvar class
Syntax hints:   β†’ wi 4   ↔ wb 205   ∧ wa 395   = wceq 1533   ∈ wcel 2098   class class class wbr 5141  dom cdm 5669  β€˜cfv 6536  DirRelcdir 18556  tailctail 18557
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1789  ax-4 1803  ax-5 1905  ax-6 1963  ax-7 2003  ax-8 2100  ax-9 2108  ax-10 2129  ax-11 2146  ax-12 2163  ax-ext 2697  ax-rep 5278  ax-sep 5292  ax-nul 5299  ax-pr 5420  ax-un 7721
This theorem depends on definitions:  df-bi 206  df-an 396  df-or 845  df-3an 1086  df-tru 1536  df-fal 1546  df-ex 1774  df-nf 1778  df-sb 2060  df-mo 2528  df-eu 2557  df-clab 2704  df-cleq 2718  df-clel 2804  df-nfc 2879  df-ne 2935  df-ral 3056  df-rex 3065  df-reu 3371  df-rab 3427  df-v 3470  df-sbc 3773  df-csb 3889  df-dif 3946  df-un 3948  df-in 3950  df-ss 3960  df-nul 4318  df-if 4524  df-sn 4624  df-pr 4626  df-op 4630  df-uni 4903  df-iun 4992  df-br 5142  df-opab 5204  df-mpt 5225  df-id 5567  df-xp 5675  df-rel 5676  df-cnv 5677  df-co 5678  df-dm 5679  df-rn 5680  df-res 5681  df-ima 5682  df-iota 6488  df-fun 6538  df-fn 6539  df-f 6540  df-f1 6541  df-fo 6542  df-f1o 6543  df-fv 6544  df-dir 18558  df-tail 18559
This theorem is referenced by:  tailfb  35769
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