题目内容
（8分）如图，E、F是□ABCD对角线
上的两点，且
.
求证：（1）
；
（2）
.
上的两点，且.求证：（1）
；（2）
.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
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分略
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