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Theorem disjss2 5031
 Description: If each element of a collection is contained in a disjoint collection, the original collection is also disjoint. (Contributed by Mario Carneiro, 14-Nov-2016.)
Assertion
Ref Expression
disjss2 (∀𝑥𝐴 𝐵𝐶 → (Disj 𝑥𝐴 𝐶Disj 𝑥𝐴 𝐵))

Proof of Theorem disjss2
Dummy variable 𝑦 is distinct from all other variables.
StepHypRef Expression
1 ssel 3965 . . . . 5 (𝐵𝐶 → (𝑦𝐵𝑦𝐶))
21ralimi 3165 . . . 4 (∀𝑥𝐴 𝐵𝐶 → ∀𝑥𝐴 (𝑦𝐵𝑦𝐶))
3 rmoim 3735 . . . 4 (∀𝑥𝐴 (𝑦𝐵𝑦𝐶) → (∃*𝑥𝐴 𝑦𝐶 → ∃*𝑥𝐴 𝑦𝐵))
42, 3syl 17 . . 3 (∀𝑥𝐴 𝐵𝐶 → (∃*𝑥𝐴 𝑦𝐶 → ∃*𝑥𝐴 𝑦𝐵))
54alimdv 1910 . 2 (∀𝑥𝐴 𝐵𝐶 → (∀𝑦∃*𝑥𝐴 𝑦𝐶 → ∀𝑦∃*𝑥𝐴 𝑦𝐵))
6 df-disj 5029 . 2 (Disj 𝑥𝐴 𝐶 ↔ ∀𝑦∃*𝑥𝐴 𝑦𝐶)
7 df-disj 5029 . 2 (Disj 𝑥𝐴 𝐵 ↔ ∀𝑦∃*𝑥𝐴 𝑦𝐵)
85, 6, 73imtr4g 297 1 (∀𝑥𝐴 𝐵𝐶 → (Disj 𝑥𝐴 𝐶Disj 𝑥𝐴 𝐵))
 Colors of variables: wff setvar class Syntax hints:   → wi 4  ∀wal 1528   ∈ wcel 2107  ∀wral 3143  ∃*wrmo 3146   ⊆ wss 3940  Disj wdisj 5028 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1789  ax-4 1803  ax-5 1904  ax-6 1963  ax-7 2008  ax-8 2109  ax-9 2117  ax-10 2138  ax-11 2153  ax-12 2169  ax-ext 2798 This theorem depends on definitions:  df-bi 208  df-an 397  df-or 844  df-tru 1533  df-ex 1774  df-nf 1778  df-sb 2063  df-mo 2620  df-clab 2805  df-cleq 2819  df-clel 2898  df-ral 3148  df-rmo 3151  df-in 3947  df-ss 3956  df-disj 5029 This theorem is referenced by:  disjeq2  5032  0disj  5055  uniioombllem2  24099  uniioombllem4  24102  disjxwwlksn  27596  disjxwwlkn  27606  fusgreghash2wspv  28028  fsumiunss  41721
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