Description: The measure of the empty set. (Contributed by Glauco Siliprandi, 11-Dec-2019)
Ref | Expression | ||
---|---|---|---|
Assertion | vol0 | |- ( vol ` (/) ) = 0 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0mbl | |- (/) e. dom vol |
|
2 | mblvol | |- ( (/) e. dom vol -> ( vol ` (/) ) = ( vol* ` (/) ) ) |
|
3 | 1 2 | ax-mp | |- ( vol ` (/) ) = ( vol* ` (/) ) |
4 | ovol0 | |- ( vol* ` (/) ) = 0 |
|
5 | 3 4 | eqtri | |- ( vol ` (/) ) = 0 |