Description: Value of a function given by the maps-to notation. (Contributed by Glauco Siliprandi, 23-Oct-2021)
Ref | Expression | ||
---|---|---|---|
Assertion | fvmpt4 | |- ( ( x e. A /\ B e. C ) -> ( ( x e. A |-> B ) ` x ) = B ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqid | |- ( x e. A |-> B ) = ( x e. A |-> B ) |
|
2 | 1 | fvmpt2 | |- ( ( x e. A /\ B e. C ) -> ( ( x e. A |-> B ) ` x ) = B ) |