Description: The domain of a composition. Exercise 27 of Enderton p. 53. (Contributed by NM, 4-Feb-2004)
Ref | Expression | ||
---|---|---|---|
Assertion | dmco | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | dfdm4 | |
|
2 | cnvco | |
|
3 | 2 | rneqi | |
4 | rnco2 | |
|
5 | dfdm4 | |
|
6 | 5 | imaeq2i | |
7 | 4 6 | eqtr4i | |
8 | 1 3 7 | 3eqtri | |