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

theorem :: REAL_1'9
  c <> 0 & a * c = b * c implies a = b
proof
  assume
A1: c<>0;
  assume a * c = b * c;
  then a * (c * c") = b * c * c" by Th4;
  then a * 1 = b * c * c" by A1,XCMPLX_0:def 7;
  then a = b * (c * c");
  then a = b * 1 by A1,XCMPLX_0:def 7;
  hence thesis;
end;
