【正文】
平面幾何的向量方法 4.(4,4) :由已知可知可設(shè) A B= B C = a ,D E = F D = b ∴ A E = A B+ B E = a + b, F C = F D + D C = b + a ∵ a+b=b+a ∴ A E = F C A E :F C 即 邊 平等且相等, ∴ AECF是平行四邊形 EC,EB,則 E C = E D + D C , E B= E A + A B C M P BB AB NB 又因 E D + E A = 0 , E C + E B = A B + D C