theorem
  mlt(i|->r1,i|->r2) = i|->(r1*r2)
proof
  reconsider s1=r1, s2=r2 as Element of REAL by XREAL_0:def 1;
  mlt(i|->s1,i|->s2) = s1*(i|->s2) by Th63
    .= i|->(r1*r2) by Th48;
  hence thesis;
end;
