let D, D9, E be non empty set ; for d9 being Element of D9
for F being Function of [:D,D9:],E holds F [:] ((<*> D),d9) = <*> E
let d9 be Element of D9; for F being Function of [:D,D9:],E holds F [:] ((<*> D),d9) = <*> E
let F be Function of [:D,D9:],E; F [:] ((<*> D),d9) = <*> E
reconsider r = F [:] ((<*> D),d9) as FinSequence of E by Th81;
len (<*> D) = 0
;
then
len r = 0
by Th82;
hence
F [:] ((<*> D),d9) = <*> E
; verum