Description: All components of the empty set are empty sets. (Contributed by Stefan O'Rear, 27-Nov-2014) (Revised by Mario Carneiro, 7-Dec-2014)
Ref | Expression | ||
---|---|---|---|
Hypothesis | str0.a | |
|
Assertion | str0 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | str0.a | |
|
2 | 0ex | |
|
3 | 2 1 | strfvn | |
4 | 0fv | |
|
5 | 3 4 | eqtr2i | |