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Theorem 3sstr4d 3202
Description: Substitution of equality into both sides of a subclass relationship. (Contributed by NM, 30-Nov-1995.) (Proof shortened by Eric Schmidt, 26-Jan-2007.)
Hypotheses
Ref Expression
3sstr4d.1 (𝜑𝐴𝐵)
3sstr4d.2 (𝜑𝐶 = 𝐴)
3sstr4d.3 (𝜑𝐷 = 𝐵)
Assertion
Ref Expression
3sstr4d (𝜑𝐶𝐷)

Proof of Theorem 3sstr4d
StepHypRef Expression
1 3sstr4d.1 . 2 (𝜑𝐴𝐵)
2 3sstr4d.2 . . 3 (𝜑𝐶 = 𝐴)
3 3sstr4d.3 . . 3 (𝜑𝐷 = 𝐵)
42, 3sseq12d 3188 . 2 (𝜑 → (𝐶𝐷𝐴𝐵))
51, 4mpbird 167 1 (𝜑𝐶𝐷)
Colors of variables: wff set class
Syntax hints:  wi 4   = wceq 1353  wss 3131
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1447  ax-7 1448  ax-gen 1449  ax-ie1 1493  ax-ie2 1494  ax-8 1504  ax-11 1506  ax-4 1510  ax-17 1526  ax-i9 1530  ax-ial 1534  ax-i5r 1535  ax-ext 2159
This theorem depends on definitions:  df-bi 117  df-nf 1461  df-sb 1763  df-clab 2164  df-cleq 2170  df-clel 2173  df-in 3137  df-ss 3144
This theorem is referenced by:  rdgss  6387  sucinc2  6450  oawordi  6473  nnnninf  7127  fzoss1  10174  fzoss2  10175  lspss  13524  clsss  13806  ntrss  13807  sslm  13935  txss12  13954  metss2lem  14185  xmettxlem  14197  xmettx  14198  nnsf  14943  nninfself  14951
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