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Theorem ssdif2d 3082
 Description: If 𝐴 is contained in 𝐵 and 𝐶 is contained in 𝐷, then (𝐴 ∖ 𝐷) is contained in (𝐵 ∖ 𝐶). 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 3080 . 2 (𝜑 → (𝐴𝐷) ⊆ (𝐴𝐶))
3 ssdifd.1 . . 3 (𝜑𝐴𝐵)
43ssdifd 3079 . 2 (𝜑 → (𝐴𝐶) ⊆ (𝐵𝐶))
52, 4sstrd 2955 1 (𝜑 → (𝐴𝐷) ⊆ (𝐵𝐶))
 Colors of variables: wff set class Syntax hints:   → wi 4   ∖ cdif 2914   ⊆ 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-in1 544  ax-in2 545  ax-io 630  ax-5 1336  ax-7 1337  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-8 1395  ax-10 1396  ax-11 1397  ax-i12 1398  ax-bndl 1399  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-tru 1246  df-nf 1350  df-sb 1646  df-clab 2027  df-cleq 2033  df-clel 2036  df-nfc 2167  df-v 2559  df-dif 2920  df-in 2924  df-ss 2931 This theorem is referenced by: (None)
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