Theorem disj1 4350

Description: Two ways of saying that two classes are disjoint (have no members in common). (Contributed by NM, 19-Aug-1993.)

Assertion

Ref	Expression
disj1	⊢ ((𝐴 ∩ 𝐵) = ∅ ↔ ∀𝑥(𝑥 ∈ 𝐴 → ¬ 𝑥 ∈ 𝐵))

Distinct variable groups:   𝑥,𝐴   𝑥,𝐵

Proof of Theorem disj1

Step	Hyp	Ref	Expression
1		disj 4347	. 2 ⊢ ((𝐴 ∩ 𝐵) = ∅ ↔ ∀𝑥 ∈ 𝐴 ¬ 𝑥 ∈ 𝐵)
2		df-ral 3075	. 2 ⊢ (∀𝑥 ∈ 𝐴 ¬ 𝑥 ∈ 𝐵 ↔ ∀𝑥(𝑥 ∈ 𝐴 → ¬ 𝑥 ∈ 𝐵))
3	1, 2	bitri 278	1 ⊢ ((𝐴 ∩ 𝐵) = ∅ ↔ ∀𝑥(𝑥 ∈ 𝐴 → ¬ 𝑥 ∈ 𝐵))

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 209  ∀wal 1536   = wceq 1538   ∈ wcel 2111  ∀wral 3070   ∩ cin 3859  ∅c0 4227

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2113  ax-9 2121  ax-ext 2729

This theorem depends on definitions:  df-bi 210  df-an 400  df-ex 1782  df-sb 2070  df-clab 2736  df-cleq 2750  df-clel 2830  df-ral 3075  df-dif 3863  df-in 3867  df-nul 4228

This theorem is referenced by:  reldisj  4351  reldisjOLD  4352  disj3  4353  undif4  4366  disjsn  4607  funun  6386  zfregs2  9221  dfac5lem4  9599  isf32lem9  9834  fzodisj  13133  fzodisjsn  13137  inpr0  30415  bnj1280  32532  ecin0  36080  zfregs2VD  41955