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Theorem ssdifss 3237
Description: Preservation of a subclass relationship by class difference. (Contributed by NM, 15-Feb-2007.)
Assertion
Ref Expression
ssdifss (𝐴𝐵 → (𝐴𝐶) ⊆ 𝐵)

Proof of Theorem ssdifss
StepHypRef Expression
1 difss 3233 . 2 (𝐴𝐶) ⊆ 𝐴
2 sstr 3136 . 2 (((𝐴𝐶) ⊆ 𝐴𝐴𝐵) → (𝐴𝐶) ⊆ 𝐵)
31, 2mpan 421 1 (𝐴𝐵 → (𝐴𝐶) ⊆ 𝐵)
Colors of variables: wff set class
Syntax hints:  wi 4  cdif 3099  wss 3102
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 604  ax-in2 605  ax-io 699  ax-5 1427  ax-7 1428  ax-gen 1429  ax-ie1 1473  ax-ie2 1474  ax-8 1484  ax-10 1485  ax-11 1486  ax-i12 1487  ax-bndl 1489  ax-4 1490  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515  ax-ext 2139
This theorem depends on definitions:  df-bi 116  df-tru 1338  df-nf 1441  df-sb 1743  df-clab 2144  df-cleq 2150  df-clel 2153  df-nfc 2288  df-v 2714  df-dif 3104  df-in 3108  df-ss 3115
This theorem is referenced by:  ssdifssd  3245
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