theorem
  mlt(i|->c1,i|->c2) = i|->(c1*c2)
proof
  reconsider s1=c1, s2=c2 as Element of COMPLEX by XCMPLX_0:def 2;
  mlt(i|->s1,i|->s2) = s1*(i|->s2) by Th27
    .= i|->(c1*c2) by Th22;
  hence thesis;
end;
