
theorem Multiply1:
  for x,y,z being positive Real holds
    (x / y) * (y / z) * (z / x) = 1
  proof
    let x,y,z be positive Real;
    (x / y) * (y / z) * (z / x) = (x / z) * (z / x) by XCMPLX_1:98
       .= x / x by XCMPLX_1:98
       .= 1 by XCMPLX_1:60;
    hence thesis;
  end;
