Description: A singleton has 0 outer Lebesgue measure. (Contributed by Mario Carneiro, 15-Aug-2014)
Ref | Expression | ||
---|---|---|---|
Assertion | ovolsn | |- ( A e. RR -> ( vol* ` { A } ) = 0 ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | snfi | |- { A } e. Fin |
|
2 | snssi | |- ( A e. RR -> { A } C_ RR ) |
|
3 | ovolfi | |- ( ( { A } e. Fin /\ { A } C_ RR ) -> ( vol* ` { A } ) = 0 ) |
|
4 | 1 2 3 | sylancr | |- ( A e. RR -> ( vol* ` { A } ) = 0 ) |