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Theorem dfss3 3004
Description: Alternate definition of subclass relationship. (Contributed by NM, 14-Oct-1999.)
Assertion
Ref Expression
dfss3 (𝐴𝐵 ↔ ∀𝑥𝐴 𝑥𝐵)
Distinct variable groups:   𝑥,𝐴   𝑥,𝐵

Proof of Theorem dfss3
StepHypRef Expression
1 dfss2 3003 . 2 (𝐴𝐵 ↔ ∀𝑥(𝑥𝐴𝑥𝐵))
2 df-ral 2360 . 2 (∀𝑥𝐴 𝑥𝐵 ↔ ∀𝑥(𝑥𝐴𝑥𝐵))
31, 2bitr4i 185 1 (𝐴𝐵 ↔ ∀𝑥𝐴 𝑥𝐵)
Colors of variables: wff set class
Syntax hints:  wi 4  wb 103  wal 1285  wcel 1436  wral 2355  wss 2988
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-5 1379  ax-7 1380  ax-gen 1381  ax-ie1 1425  ax-ie2 1426  ax-8 1438  ax-11 1440  ax-4 1443  ax-17 1462  ax-i9 1466  ax-ial 1470  ax-i5r 1471  ax-ext 2067
This theorem depends on definitions:  df-bi 115  df-nf 1393  df-sb 1690  df-clab 2072  df-cleq 2078  df-clel 2081  df-ral 2360  df-in 2994  df-ss 3001
This theorem is referenced by:  ssrab  3088  eqsnm  3584  uni0b  3663  uni0c  3664  ssint  3689  ssiinf  3764  sspwuni  3797  dftr3  3917  tfis  4373  rninxp  4842  fnres  5097  eqfnfv3  5364  funimass3  5380  ffvresb  5426  tfrlemibxssdm  6048  tfr1onlembxssdm  6064  tfrcllembxssdm  6077  bdss  11224
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