reserve a,b,r for Real;
reserve A,B for non empty set;
reserve f,g,h for Element of PFuncs(A,REAL);

theorem Th11:
  (addpfunc A).(f,(addpfunc A).(g,h)) = (addpfunc A).((addpfunc A) .(f,g),h)
by RFUNCT_3:15,BINOP_1:def 3;
