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Theorem psseq12i 3731
Description: An equality inference for the proper subclass relationship. (Contributed by NM, 9-Jun-2004.)
Hypotheses
Ref Expression
psseq1i.1 𝐴 = 𝐵
psseq12i.2 𝐶 = 𝐷
Assertion
Ref Expression
psseq12i (𝐴𝐶𝐵𝐷)

Proof of Theorem psseq12i
StepHypRef Expression
1 psseq1i.1 . . 3 𝐴 = 𝐵
21psseq1i 3729 . 2 (𝐴𝐶𝐵𝐶)
3 psseq12i.2 . . 3 𝐶 = 𝐷
43psseq2i 3730 . 2 (𝐵𝐶𝐵𝐷)
52, 4bitri 264 1 (𝐴𝐶𝐵𝐷)
Colors of variables: wff setvar class
Syntax hints:  wb 196   = wceq 1523  wpss 3608
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1762  ax-4 1777  ax-5 1879  ax-6 1945  ax-7 1981  ax-9 2039  ax-10 2059  ax-11 2074  ax-12 2087  ax-13 2282  ax-ext 2631
This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  df-tru 1526  df-ex 1745  df-nf 1750  df-sb 1938  df-clab 2638  df-cleq 2644  df-clel 2647  df-ne 2824  df-in 3614  df-ss 3621  df-pss 3623
This theorem is referenced by: (None)
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