let X, A be set ; :: thesis: ( chi (A,X) is without+infty & chi (A,X) is without-infty )
rng (chi (A,X)) c= {0,1} by FUNCT_3:39;
then ( not +infty in rng (chi (A,X)) & not -infty in rng (chi (A,X)) ) ;
hence ( chi (A,X) is without+infty & chi (A,X) is without-infty ) by MESFUNC5:def 3, MESFUNC5:def 4; :: thesis: verum