题目内容
(本题满分10分)如图,在梯形中,两点在边上,且四边形是平行四边形.
(1)与有何等量关系?请说明理由;
(2)当时,求证:是矩形.
【答案】
(1)解:.························································································ (1分)
理由如下:
,
四边形和四边形都是平行四边形.
.
又四边形是平行四边形,.
.
.···································································································· (5分)
(2)证明:四边形和四边形都是平行四边形,
.
.
又四边形是平行四边形,四边形是矩形
【解析】略
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