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

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