reserve a,b,c,d,e for Real;

theorem Th06:
  a <> 0 implies a * (b / (2 * a)) = b / 2
  proof
    assume
A1: a <> 0;
    a * (b / (2 * a)) = (a * b) / (a * 2) by XCMPLX_1:74
                     .= (a / a * b) / 2 by XCMPLX_1:83
                     .= (1 * b) / 2 by A1,XCMPLX_1:60;
    hence thesis;
  end;
