reserve A,B,C,Y,x,y,z for set, U, D for non empty set,
X for non empty Subset of D, d,d1,d2 for Element of D;
reserve P,Q,R for Relation, g for Function, p,q for FinSequence;
reserve f for BinOp of D, i,m,n for Nat;

theorem Th14:
for d being non empty Element of D** holds
D-multiCat.d=(MultPlace(D-concatenation)).d
proof
let d be non empty Element of D**; set f=D-concatenation, F=D-multiCat;
not d in {{}} by TARSKI:def 1; then
d in D**\{{}} by XBOOLE_0:def 5; hence
F.d = (F|(D**\{{}})).d by FUNCT_1:49 .= (MultPlace(f)).d by Lm23;
end;
