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Theorem ssdifss 3176
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 3172 . 2 (𝐴𝐶) ⊆ 𝐴
2 sstr 3075 . 2 (((𝐴𝐶) ⊆ 𝐴𝐴𝐵) → (𝐴𝐶) ⊆ 𝐵)
31, 2mpan 420 1 (𝐴𝐵 → (𝐴𝐶) ⊆ 𝐵)
Colors of variables: wff set class
Syntax hints:  wi 4  cdif 3038  wss 3041
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 588  ax-in2 589  ax-io 683  ax-5 1408  ax-7 1409  ax-gen 1410  ax-ie1 1454  ax-ie2 1455  ax-8 1467  ax-10 1468  ax-11 1469  ax-i12 1470  ax-bndl 1471  ax-4 1472  ax-17 1491  ax-i9 1495  ax-ial 1499  ax-i5r 1500  ax-ext 2099
This theorem depends on definitions:  df-bi 116  df-tru 1319  df-nf 1422  df-sb 1721  df-clab 2104  df-cleq 2110  df-clel 2113  df-nfc 2247  df-v 2662  df-dif 3043  df-in 3047  df-ss 3054
This theorem is referenced by:  ssdifssd  3184
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