並前往http://www.nowforyou.com/math/%E8%AA%B2%E6%9C%ACPPT/6-2-1%E6%AC%A1%E6%95%B8%E5%88%86%E9%85%8D%E8%88%87%E8%B3%87%E6%96%99%E5%B1%95%E7%A4%BA.pps
