Theorem disjxsn 5083

Description: A singleton collection is disjoint. (Contributed by Mario Carneiro, 14-Nov-2016.)

Assertion

Ref	Expression
disjxsn	⊢ Disj 𝑥 ∈ {𝐴}𝐵

Distinct variable group:   𝑥,𝐴

Allowed substitution hint:   𝐵(𝑥)

Proof of Theorem disjxsn

Dummy variable 𝑦 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		dfdisj2 5058	. 2 ⊢ (Disj 𝑥 ∈ {𝐴}𝐵 ↔ ∀𝑦∃*𝑥(𝑥 ∈ {𝐴} ∧ 𝑦 ∈ 𝐵))
2		moeq 3664	. . 3 ⊢ ∃*𝑥 𝑥 = 𝐴
3		elsni 4591	. . . . 5 ⊢ (𝑥 ∈ {𝐴} → 𝑥 = 𝐴)
4	3	adantr 480	. . . 4 ⊢ ((𝑥 ∈ {𝐴} ∧ 𝑦 ∈ 𝐵) → 𝑥 = 𝐴)
5	4	moimi 2539	. . 3 ⊢ (∃*𝑥 𝑥 = 𝐴 → ∃*𝑥(𝑥 ∈ {𝐴} ∧ 𝑦 ∈ 𝐵))
6	2, 5	ax-mp 5	. 2 ⊢ ∃*𝑥(𝑥 ∈ {𝐴} ∧ 𝑦 ∈ 𝐵)
7	1, 6	mpgbir 1800	1 ⊢ Disj 𝑥 ∈ {𝐴}𝐵

Syntax hints:   ∧ wa 395   = wceq 1541   ∈ wcel 2110  ∃*wmo 2532  {csn 4574  Disj wdisj 5056

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796  ax-4 1810  ax-5 1911  ax-6 1968  ax-7 2009  ax-8 2112  ax-9 2120  ax-ext 2702

This theorem depends on definitions:  df-bi 207  df-an 396  df-tru 1544  df-ex 1781  df-sb 2067  df-mo 2534  df-clab 2709  df-cleq 2722  df-clel 2804  df-rmo 3344  df-sn 4575  df-disj 5057

This theorem is referenced by:  disjx0  5084  disjdifprg  32545  rossros  34183  meadjun  46479