Theorem difprsn2 4774

Description: Removal of a singleton from an unordered pair. (Contributed by Alexander van der Vekens, 5-Oct-2017.)

Assertion

Ref	Expression
difprsn2	⊢ (𝐴 ≠ 𝐵 → ({𝐴, 𝐵} ∖ {𝐵}) = {𝐴})

Proof of Theorem difprsn2

Step	Hyp	Ref	Expression
1		prcom 4703	. . 3 ⊢ {𝐴, 𝐵} = {𝐵, 𝐴}
2	1	difeq1i 4080	. 2 ⊢ ({𝐴, 𝐵} ∖ {𝐵}) = ({𝐵, 𝐴} ∖ {𝐵})
3		necom 3014	. . 3 ⊢ (𝐴 ≠ 𝐵 ↔ 𝐵 ≠ 𝐴)
4		difprsn1 4773	. . 3 ⊢ (𝐵 ≠ 𝐴 → ({𝐵, 𝐴} ∖ {𝐵}) = {𝐴})
5	3, 4	sylbi 220	. 2 ⊢ (𝐴 ≠ 𝐵 → ({𝐵, 𝐴} ∖ {𝐵}) = {𝐴})
6	2, 5	eqtrid 2813	1 ⊢ (𝐴 ≠ 𝐵 → ({𝐴, 𝐵} ∖ {𝐵}) = {𝐴})

This proof depends on syntax axioms:   → wi 4   = wceq 1570   ≠ wne 2961   ∖ cdif 3905  {csn 4594  {cpr 4596

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-8 2148  ax-9 2156  ax-ext 2738

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-tru 1573  df-fal 1583  df-ex 1813  df-sb 2100  df-clab 2745  df-cleq 2758  df-clel 2841  df-ne 2962  df-ral 3083  df-rab 3420  df-v 3460  df-dif 3911  df-un 3913  df-in 3915  df-nul 4290  df-sn 4595  df-pr 4597

This theorem is used by:  f12dfv  7282  pmtrprfval  19588  nbgr2vtx1edg  29737  nbuhgr2vtx1edgb  29739  nfrgr2v  30660  indsupp  33224  cycpm2tr  33470  drngmxidl  33790  ldepsnlinc  49329