Theorem wundif 10709

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 4133	. 2 ⊢ (𝜑 → (𝐴 ∖ 𝐵) ⊆ 𝐴)
4	1, 2, 3	wunss 10707	1 ⊢ (𝜑 → (𝐴 ∖ 𝐵) ∈ 𝑈)

Syntax hints:   → wi 4   ∈ wcel 2107   ∖ cdif 3946  WUnicwun 10695

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  ax-sep 5300

This theorem depends on definitions:  df-bi 206  df-an 398  df-3an 1090  df-tru 1545  df-ex 1783  df-sb 2069  df-clab 2711  df-cleq 2725  df-clel 2811  df-ne 2942  df-ral 3063  df-rex 3072  df-rab 3434  df-v 3477  df-dif 3952  df-in 3956  df-ss 3966  df-pw 4605  df-uni 4910  df-tr 5267  df-wun 10697

This theorem is referenced by:  wuncn  11165