Description: Two ways to say that A is a nonzero number of the set B . (Contributed by Mario Carneiro, 21-May-2015)
Ref | Expression | ||
---|---|---|---|
Assertion | dif1o | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df1o2 | |
|
2 | 1 | difeq2i | |
3 | 2 | eleq2i | |
4 | eldifsn | |
|
5 | 3 4 | bitri | |