let C be Category; for I being Indexing of C
for T being TargetCat of I holds pr2 (I -functor C,T) = I `2
let I be Indexing of C; for T being TargetCat of I holds pr2 (I -functor C,T) = I `2
let T be TargetCat of I; pr2 (I -functor C,T) = I `2
A1:
dom (I -functor C,T) = the carrier' of C
by FUNCT_2:def 1;
( dom (pr2 (I -functor C,T)) = dom (I -functor C,T) & dom (I `2 ) = the carrier' of C )
by MCART_1:def 13, PARTFUN1:def 4;
hence
pr2 (I -functor C,T) = I `2
by A1, A2, FUNCT_1:9; verum