Theorem unss12 4183

Description: Subclass law for union of classes. (Contributed by NM, 2-Jun-2004.)

Assertion

Ref	Expression
unss12	⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐶 ⊆ 𝐷) → (𝐴 ∪ 𝐶) ⊆ (𝐵 ∪ 𝐷))

Proof of Theorem unss12

Step	Hyp	Ref	Expression
1		unss1 4180	. 2 ⊢ (𝐴 ⊆ 𝐵 → (𝐴 ∪ 𝐶) ⊆ (𝐵 ∪ 𝐶))
2		unss2 4182	. 2 ⊢ (𝐶 ⊆ 𝐷 → (𝐵 ∪ 𝐶) ⊆ (𝐵 ∪ 𝐷))
3	1, 2	sylan9ss 3996	1 ⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐶 ⊆ 𝐷) → (𝐴 ∪ 𝐶) ⊆ (𝐵 ∪ 𝐷))

Syntax hints:   → wi 4   ∧ wa 397   ∪ cun 3947   ⊆ wss 3949

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2109  ax-9 2117  ax-ext 2704

This theorem depends on definitions:  df-bi 206  df-an 398  df-or 847  df-tru 1545  df-ex 1783  df-sb 2069  df-clab 2711  df-cleq 2725  df-clel 2811  df-v 3477  df-un 3954  df-in 3956  df-ss 3966

This theorem is referenced by:  pwssun  5572  fun  6754  f1un  6854  undomOLD  9060  finsschain  9359  trclun  14961  relexpfld  14996  mulgfval  18952  mvdco  19313  dprd2da  19912  dmdprdsplit2lem  19915  lspun  20598  mulsproplem13  27587  mulsproplem14  27588  spanuni  30828  sshhococi  30830  mthmpps  34604  pibt2  36346  mblfinlem3  36575  dochdmj1  40309  mptrcllem  42412  clcnvlem  42422  dfrcl2  42473  relexpss1d  42504  corclrcl  42506  relexp0a  42515  corcltrcl  42538  frege131d  42563