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Theorem ssiun2s 3757
Description: Subset relationship for an indexed union. (Contributed by NM, 26-Oct-2003.)
Hypothesis
Ref Expression
ssiun2s.1 (𝑥 = 𝐶𝐵 = 𝐷)
Assertion
Ref Expression
ssiun2s (𝐶𝐴𝐷 𝑥𝐴 𝐵)
Distinct variable groups:   𝑥,𝐴   𝑥,𝐶   𝑥,𝐷
Allowed substitution hint:   𝐵(𝑥)

Proof of Theorem ssiun2s
StepHypRef Expression
1 nfcv 2225 . 2 𝑥𝐶
2 nfcv 2225 . . 3 𝑥𝐷
3 nfiu1 3743 . . 3 𝑥 𝑥𝐴 𝐵
42, 3nfss 3007 . 2 𝑥 𝐷 𝑥𝐴 𝐵
5 ssiun2s.1 . . 3 (𝑥 = 𝐶𝐵 = 𝐷)
65sseq1d 3042 . 2 (𝑥 = 𝐶 → (𝐵 𝑥𝐴 𝐵𝐷 𝑥𝐴 𝐵))
7 ssiun2 3756 . 2 (𝑥𝐴𝐵 𝑥𝐴 𝐵)
81, 4, 6, 7vtoclgaf 2677 1 (𝐶𝐴𝐷 𝑥𝐴 𝐵)
Colors of variables: wff set class
Syntax hints:  wi 4   = wceq 1287  wcel 1436  wss 2988   ciun 3713
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-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-ral 2360  df-rex 2361  df-v 2617  df-in 2994  df-ss 3001  df-iun 3715
This theorem is referenced by: (None)
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