let C1, C2, C3 be non empty set ; :: thesis: for f being RMembership_Func of C1,C2 holds f (#) (Zmf C2,C3) = Zmf C1,C3
let f be RMembership_Func of C1,C2; :: thesis: f (#) (Zmf C2,C3) = Zmf C1,C3
A1: dom (Zmf C1,C3) = [:C1,C3:] by FUNCT_2:def 1;
A2: for c being Element of [:C1,C3:] st c in [:C1,C3:] holds
(f (#) (Zmf C2,C3)) . c = (Zmf C1,C3) . c

proof

let c be Element of [:C1,C3:]; :: thesis: ( c in [:C1,C3:] implies (f (#) (Zmf C2,C3)) . c = (Zmf C1,C3) . c )
consider x, z being set such that
A3: x in C1 and
A4: z in C3 and
A5: c = [x,z] by ZFMISC_1:def 2;
(f (#) (Zmf C2,C3)) . c = (f (#) (Zmf C2,C3)) . x,z by A5
.= sup (rng (min f,(Zmf C2,C3),x,z)) by A5, Def3
.= (Zmf C1,C3) . c by A3, A4, A5, Lm7 ;
hence ( c in [:C1,C3:] implies (f (#) (Zmf C2,C3)) . c = (Zmf C1,C3) . c ) ; :: thesis: verum

end;

dom (f (#) (Zmf C2,C3)) = [:C1,C3:] by FUNCT_2:def 1;
hence f (#) (Zmf C2,C3) = Zmf C1,C3 by A1, A2, PARTFUN1:34; :: thesis: verum