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Mirrors > Home > NFE Home > Th. List > ssun3 | GIF version |
Description: Subclass law for union of classes. (Contributed by NM, 5-Aug-1993.) |
Ref | Expression |
---|---|
ssun3 | ⊢ (A ⊆ B → A ⊆ (B ∪ C)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ssun1 3426 | . 2 ⊢ B ⊆ (B ∪ C) | |
2 | sstr2 3279 | . 2 ⊢ (A ⊆ B → (B ⊆ (B ∪ C) → A ⊆ (B ∪ C))) | |
3 | 1, 2 | mpi 16 | 1 ⊢ (A ⊆ B → A ⊆ (B ∪ C)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∪ cun 3207 ⊆ wss 3257 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1546 ax-5 1557 ax-17 1616 ax-9 1654 ax-8 1675 ax-6 1729 ax-7 1734 ax-11 1746 ax-12 1925 ax-ext 2334 |
This theorem depends on definitions: df-bi 177 df-or 359 df-an 360 df-nan 1288 df-tru 1319 df-ex 1542 df-nf 1545 df-sb 1649 df-clab 2340 df-cleq 2346 df-clel 2349 df-nfc 2478 df-v 2861 df-nin 3211 df-compl 3212 df-in 3213 df-un 3214 df-ss 3259 |
This theorem is referenced by: ssun 3442 ssunsn2 3865 pwadjoin 4119 |
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