Description: Split off the first element of an unordered triple. (Contributed by Mario Carneiro, 5-Jan-2016)
Ref | Expression | ||
---|---|---|---|
Assertion | tpass | |- { A , B , C } = ( { A } u. { B , C } ) |
Step | Hyp | Ref | Expression |
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1 | df-tp | |- { B , C , A } = ( { B , C } u. { A } ) |
|
2 | tprot | |- { A , B , C } = { B , C , A } |
|
3 | uncom | |- ( { A } u. { B , C } ) = ( { B , C } u. { A } ) |
|
4 | 1 2 3 | 3eqtr4i | |- { A , B , C } = ( { A } u. { B , C } ) |