题干

如图1,正方形纸片ABCD的边长为2,翻折∠B、∠D,使两个直角的顶点重合于对角线BD上一点P,EF、GH分别是折痕(如图2).设AE=x(0<x<2),给出下列判断:

①当x=1时,点P是正方形ABCD的中心;

②当x=

1
2
时,EF+GH>AC;

③当0<x<2时,六边形AEFCHG面积的最大值是

11
4

④当0<x<2时,六边形AEFCHG周长的值不变.

其中正确的是____(写出所有正确判断的序号).

上一题 下一题 0.0难度 选择题 更新时间:2010-10-22 10:05:53

答案(点此获取答案解析)

①④

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阅读理解

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    Like most children, Tegan was having a good time playing with all the toys that were different from her own and that were kept for children to play with at her grandparents' house. In particular, Tegan had found a little tea set and had begun pretending that she was having a tea party. She set up all the place settings and arranged her table with the great care and elegance that only a three-year-old can create. Meanwhile, her Daddy concentrated on conversation, and as he continued to chat with his family, Tegan would hand him a cup of "tea". Her Daddy, who always tries to participate in her games, would pause for a few seconds from his conversation, and say all the proper words and gestures for her tea party which would thrill Tegan. He would request two lumps of sugar. He would tell her how wonderful her tea tasted, and then he would continue his adult conversation with his family.

    After going through this routine several times, her Daddy suddenly awoke to reality as he had a flash of concern in his mind: "She is only three years old, where is she getting this 'tea' that I've been dutifully drinking?" He quietly followed her, without her knowing, and his fears were growing stronger as he saw her turn and go through the bathroom door. Sure enough, there she was stretching up on her tippy toes reaching up to get her 'tea' water out of the container of water that grandpa used to soak (浸泡)his false teeth!

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风景旧曾谙。

___________,

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能不忆江南?

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如图,一艘核潜艇在海面DF下600米A点处测得俯角为30°正前方的海底C点处有黑匣子,继续在同一深度直线航行1464米到B点处测得正前方C点处的俯角为45°.求海底C点处距离海面DF的深度(结果精确到个位,参考数据: 2 ≈1.414, 3 ≈1.732, 5 ≈2.236)

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