reserve a,b,c,d for Real;
reserve r,s for Real;

theorem
  b < 0 & b < -a implies -1 < a/b
proof
  assume that
A1: b < 0 and
A2: b < -a;
  assume a/b <= -1;
  then a/b*b >= (-1)*b by A1,Lm28;
  then a >= -b by A1,XCMPLX_1:87;
  hence thesis by A2,Th26;
end;
