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Theorem 3sstr3i 4019
Description: Substitution of equality in both sides of a subclass relationship. (Contributed by NM, 13-Jan-1996.) (Proof shortened by Eric Schmidt, 26-Jan-2007.)
Hypotheses
Ref Expression
3sstr3.1 𝐴𝐵
3sstr3.2 𝐴 = 𝐶
3sstr3.3 𝐵 = 𝐷
Assertion
Ref Expression
3sstr3i 𝐶𝐷

Proof of Theorem 3sstr3i
StepHypRef Expression
1 3sstr3.1 . 2 𝐴𝐵
2 3sstr3.2 . . 3 𝐴 = 𝐶
3 3sstr3.3 . . 3 𝐵 = 𝐷
42, 3sseq12i 4007 . 2 (𝐴𝐵𝐶𝐷)
51, 4mpbi 229 1 𝐶𝐷
Colors of variables: wff setvar class
Syntax hints:   = wceq 1533  wss 3943
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-ext 2697
This theorem depends on definitions:  df-bi 206  df-an 396  df-tru 1536  df-ex 1774  df-sb 2060  df-clab 2704  df-cleq 2718  df-clel 2804  df-v 3470  df-in 3950  df-ss 3960
This theorem is referenced by:  ttrclco  9715  cottrcl  9716  odf1o2  19493  leordtval2  23071  uniiccvol  25464  ballotlem2  34017  cotrcltrcl  43049
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