Description: If the operation value of a class for an argument is a set, the class restricted to the singleton of the argument is a function. (Contributed by Alexander van der Vekens, 26-May-2017)
Ref | Expression | ||
---|---|---|---|
Assertion | aovvfunressn | |- ( (( A F B )) e. C -> Fun ( F |` { <. A , B >. } ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-aov | |- (( A F B )) = ( F ''' <. A , B >. ) |
|
2 | 1 | eleq1i | |- ( (( A F B )) e. C <-> ( F ''' <. A , B >. ) e. C ) |
3 | afvvfunressn | |- ( ( F ''' <. A , B >. ) e. C -> Fun ( F |` { <. A , B >. } ) ) |
|
4 | 2 3 | sylbi | |- ( (( A F B )) e. C -> Fun ( F |` { <. A , B >. } ) ) |