Theorem unabs 3437

Description: Absorption law for union. (Contributed by NM, 16-Apr-2006.)

Assertion

Ref	Expression
unabs	⊢ (𝐴 ∪ (𝐴 ∩ 𝐵)) = 𝐴

Proof of Theorem unabs

Step	Hyp	Ref	Expression
1		inss1 3426	. 2 ⊢ (𝐴 ∩ 𝐵) ⊆ 𝐴
2		ssequn2 3379	. 2 ⊢ ((𝐴 ∩ 𝐵) ⊆ 𝐴 ↔ (𝐴 ∪ (𝐴 ∩ 𝐵)) = 𝐴)
3	1, 2	mpbi 145	1 ⊢ (𝐴 ∪ (𝐴 ∩ 𝐵)) = 𝐴

Syntax hints:   = wceq 1397   ∪ cun 3197   ∩ cin 3198   ⊆ wss 3199

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 716  ax-5 1495  ax-7 1496  ax-gen 1497  ax-ie1 1541  ax-ie2 1542  ax-8 1552  ax-10 1553  ax-11 1554  ax-i12 1555  ax-bndl 1557  ax-4 1558  ax-17 1574  ax-i9 1578  ax-ial 1582  ax-i5r 1583  ax-ext 2212

This theorem depends on definitions:  df-bi 117  df-tru 1400  df-nf 1509  df-sb 1810  df-clab 2217  df-cleq 2223  df-clel 2226  df-nfc 2362  df-v 2803  df-un 3203  df-in 3205  df-ss 3212

This theorem is referenced by: (None)