theorem
  Product ((i+j) |->c) = (Product (i|->c))*(Product (j|->c))
proof
  reconsider s=c as Element of COMPLEX by XCMPLX_0:def 2;
  Product ((i+j) |->s) =
    multcomplex.(multcomplex$$(i|->s),multcomplex$$(j|->s)) by SETWOP_2:26
    .= (Product (i|->s))*(Product (j|->s)) by BINOP_2:def 5;
  hence thesis;
end;
