Theorem wundif 10667

Description: A weak universe is closed under class difference. (Contributed by Mario Carneiro, 2-Jan-2017.)

Hypotheses

Ref	Expression
wununi.1	⊢ (𝜑 → 𝑈 ∈ WUni)
wununi.2	⊢ (𝜑 → 𝐴 ∈ 𝑈)

Assertion

Ref	Expression
wundif	⊢ (𝜑 → (𝐴 ∖ 𝐵) ∈ 𝑈)

Proof of Theorem wundif

Step	Hyp	Ref	Expression
1		wununi.1	. 2 ⊢ (𝜑 → 𝑈 ∈ WUni)
2		wununi.2	. 2 ⊢ (𝜑 → 𝐴 ∈ 𝑈)
3		difssd 4100	. 2 ⊢ (𝜑 → (𝐴 ∖ 𝐵) ⊆ 𝐴)
4	1, 2, 3	wunss 10665	1 ⊢ (𝜑 → (𝐴 ∖ 𝐵) ∈ 𝑈)

Syntax hints:   → wi 4   ∈ wcel 2109   ∖ cdif 3911  WUnicwun 10653

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1795  ax-4 1809  ax-5 1910  ax-6 1967  ax-7 2008  ax-8 2111  ax-9 2119  ax-ext 2701  ax-sep 5251

This theorem depends on definitions:  df-bi 207  df-an 396  df-3an 1088  df-tru 1543  df-ex 1780  df-sb 2066  df-clab 2708  df-cleq 2721  df-clel 2803  df-ne 2926  df-ral 3045  df-rex 3054  df-rab 3406  df-v 3449  df-dif 3917  df-in 3921  df-ss 3931  df-pw 4565  df-uni 4872  df-tr 5215  df-wun 10655

This theorem is referenced by:  wuncn  11123