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Theorem 3sstr3i 3792
 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 3780 . 2 (𝐴𝐵𝐶𝐷)
51, 4mpbi 220 1 𝐶𝐷
 Colors of variables: wff setvar class Syntax hints:   = wceq 1631   ⊆ wss 3723 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1870  ax-4 1885  ax-5 1991  ax-6 2057  ax-7 2093  ax-9 2154  ax-10 2174  ax-11 2190  ax-12 2203  ax-ext 2751 This theorem depends on definitions:  df-bi 197  df-an 383  df-or 837  df-tru 1634  df-ex 1853  df-nf 1858  df-sb 2050  df-clab 2758  df-cleq 2764  df-clel 2767  df-in 3730  df-ss 3737 This theorem is referenced by:  odf1o2  18195  leordtval2  21237  uniiccvol  23568  ballotlem2  30890  cotrcltrcl  38543
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