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Theorem ssdif2d 3125
Description: If 𝐴 is contained in 𝐵 and 𝐶 is contained in 𝐷, then (𝐴𝐷) is contained in (𝐵𝐶). Deduction form. (Contributed by David Moews, 1-May-2017.)
Hypotheses
Ref Expression
ssdifd.1 (𝜑𝐴𝐵)
ssdif2d.2 (𝜑𝐶𝐷)
Assertion
Ref Expression
ssdif2d (𝜑 → (𝐴𝐷) ⊆ (𝐵𝐶))

Proof of Theorem ssdif2d
StepHypRef Expression
1 ssdif2d.2 . . 3 (𝜑𝐶𝐷)
21sscond 3123 . 2 (𝜑 → (𝐴𝐷) ⊆ (𝐴𝐶))
3 ssdifd.1 . . 3 (𝜑𝐴𝐵)
43ssdifd 3122 . 2 (𝜑 → (𝐴𝐶) ⊆ (𝐵𝐶))
52, 4sstrd 3022 1 (𝜑 → (𝐴𝐷) ⊆ (𝐵𝐶))
Colors of variables: wff set class
Syntax hints:  wi 4  cdif 2983  wss 2986
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-in1 577  ax-in2 578  ax-io 663  ax-5 1379  ax-7 1380  ax-gen 1381  ax-ie1 1425  ax-ie2 1426  ax-8 1438  ax-10 1439  ax-11 1440  ax-i12 1441  ax-bndl 1442  ax-4 1443  ax-17 1462  ax-i9 1466  ax-ial 1470  ax-i5r 1471  ax-ext 2067
This theorem depends on definitions:  df-bi 115  df-tru 1290  df-nf 1393  df-sb 1690  df-clab 2072  df-cleq 2078  df-clel 2081  df-nfc 2214  df-v 2616  df-dif 2988  df-in 2992  df-ss 2999
This theorem is referenced by: (None)
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