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

theorem
  0 < b & -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,Lm12;
  then a <= -b by A1,XCMPLX_1:87;
  hence thesis by A2,Th25;
end;
