Theorem fnprg

Description: Function with a domain of two different values. (Contributed by FL, 26-Jun-2011) (Revised by Mario Carneiro, 26-Apr-2015)

	Ref	Expression
Assertion	fnprg	|- ( ( ( A e. V /\ B e. W ) /\ ( C e. X /\ D e. Y ) /\ A =/= B ) -> { <. A , C >. , <. B , D >. } Fn { A , B } )

Proof

Step	Hyp	Ref	Expression
1		funprg	|- ( ( ( A e. V /\ B e. W ) /\ ( C e. X /\ D e. Y ) /\ A =/= B ) -> Fun { <. A , C >. , <. B , D >. } )
2		dmpropg	|- ( ( C e. X /\ D e. Y ) -> dom { <. A , C >. , <. B , D >. } = { A , B } )
3	2	3ad2ant2	|- ( ( ( A e. V /\ B e. W ) /\ ( C e. X /\ D e. Y ) /\ A =/= B ) -> dom { <. A , C >. , <. B , D >. } = { A , B } )
4		df-fn	|- ( { <. A , C >. , <. B , D >. } Fn { A , B } <-> ( Fun { <. A , C >. , <. B , D >. } /\ dom { <. A , C >. , <. B , D >. } = { A , B } ) )
5	1 3 4	sylanbrc	|- ( ( ( A e. V /\ B e. W ) /\ ( C e. X /\ D e. Y ) /\ A =/= B ) -> { <. A , C >. , <. B , D >. } Fn { A , B } )