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Theorem eqsstr3d 2980
 Description: Substitution of equality into a subclass relationship. (Contributed by NM, 25-Apr-2004.)
Hypotheses
Ref Expression
eqsstr3d.1 (𝜑𝐵 = 𝐴)
eqsstr3d.2 (𝜑𝐵𝐶)
Assertion
Ref Expression
eqsstr3d (𝜑𝐴𝐶)

Proof of Theorem eqsstr3d
StepHypRef Expression
1 eqsstr3d.1 . . 3 (𝜑𝐵 = 𝐴)
21eqcomd 2045 . 2 (𝜑𝐴 = 𝐵)
3 eqsstr3d.2 . 2 (𝜑𝐵𝐶)
42, 3eqsstrd 2979 1 (𝜑𝐴𝐶)
 Colors of variables: wff set class Syntax hints:   → wi 4   = wceq 1243   ⊆ wss 2917 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-5 1336  ax-7 1337  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-8 1395  ax-11 1397  ax-4 1400  ax-17 1419  ax-i9 1423  ax-ial 1427  ax-i5r 1428  ax-ext 2022 This theorem depends on definitions:  df-bi 110  df-nf 1350  df-sb 1646  df-clab 2027  df-cleq 2033  df-clel 2036  df-in 2924  df-ss 2931 This theorem is referenced by:  ssxpbm  4756  ssxp1  4757  ssxp2  4758  suppssof1  5728  tfrlemiubacc  5944  oaword1  6050  phplem4dom  6324  archnqq  6515
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