题目

（8分）如图，E、F是□ABCD对角线上的两点，且.求证：（1）；（2）.  答案：证明：（1）四边形是平行四边形，..······································································································ 2分，..······································································································ 3分··························································································· 4分(2)由得.，···························································································· 5分四边形是平行四边形. ··················································································· 7分.  8分解析:略 

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