Description: The empty set maps one-to-one into any class, deduction version. (Contributed by AV, 25-Nov-2020)
Ref | Expression | ||
---|---|---|---|
Hypothesis | f10d.f | |
|
Assertion | f10d | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | f10d.f | |
|
2 | f10 | |
|
3 | dm0 | |
|
4 | f1eq2 | |
|
5 | 3 4 | ax-mp | |
6 | 2 5 | mpbir | |
7 | 1 | dmeqd | |
8 | eqidd | |
|
9 | 1 7 8 | f1eq123d | |
10 | 6 9 | mpbiri | |