並前往http://math.ymhs.tyc.edu.tw/chenjt99/ScrClass/1072/%E9%AB%98%E4%B8%89%E9%81%B8%E4%BF%AE%E4%B9%99%E4%B8%8B/%E7%BF%92%E4%BD%9C/1.2.pdf