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Theorem snprss2 4121

Description: A singleton is a subset of an unordered pair. (Contributed by SF, 12-Jan-2015.)

**Assertion**
Ref	Expression
snprss2	⊢ {A} ⊆ {B, A}

**Proof of Theorem snprss2**
Step	Hyp	Ref	Expression
1		snprss1 4120	. 2 ⊢ {A} ⊆ {A, B}
2		prcom 3798	. 2 ⊢ {A, B} = {B, A}
3	1, 2	sseqtri 3303	1 ⊢ {A} ⊆ {B, A}

Colors of variables: wff setvar class

Syntax hints: ⊆ wss 3257 {csn 3737 {cpr 3738

This theorem was proved from axioms: ax-1 5 ax-2 6 ax-3 7 ax-mp 8 ax-gen 1546 ax-5 1557 ax-17 1616 ax-9 1654 ax-8 1675 ax-6 1729 ax-7 1734 ax-11 1746 ax-12 1925 ax-ext 2334

This theorem depends on definitions: df-bi 177 df-or 359 df-an 360 df-nan 1288 df-tru 1319 df-ex 1542 df-nf 1545 df-sb 1649 df-clab 2340 df-cleq 2346 df-clel 2349 df-nfc 2478 df-v 2861 df-nin 3211 df-compl 3212 df-in 3213 df-un 3214 df-ss 3259 df-pr 3742

This theorem is referenced by: (None)