(1)依题意,BO=1,CO=2,BC=3,AB^2+BC^2=13,解得AB=k=-2(正值舍去);
(2)三角形AOC的面积=CO*AB/2=2*2/2=2;
(3)n=-2/m,所以S=0.5*3I-2/mI=3/m.