let x be set ; :: according to VALUED_0:def 10 :: thesis: ( not x in dom (r (#) f) or (r (#) f) . x is rational )
assume x in dom (r (#) f) ; :: thesis: (r (#) f) . x is rational
then (r (#) f) . x = r * (f . x) by Def5;
hence (r (#) f) . x is rational ; :: thesis: verum