Description: A function is a union of singletons of ordered pairs indexed by its domain. (Contributed by AV, 18-Sep-2020)
Ref | Expression | ||
---|---|---|---|
Assertion | funiun | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | funfn | |
|
2 | dffn5 | |
|
3 | 1 2 | sylbb | |
4 | fvex | |
|
5 | 4 | dfmpt | |
6 | 3 5 | eqtrdi | |