如图.在Rt△ABC中,∠B=90°,AC=60cm,∠A=60°,点D从点A出发沿AC方向以4cm∕秒的速度向点C匀速运动,同时点E从点B出发沿BA方向以2cm∕秒的速度向点A匀速运动,设点D、E运动的时间是t秒(0<t<15),过点D作DF⊥BC于点F,连接DE、EF.
(1)求证:四边形AEFD是平行四边形;
(2)当t为何值时,动点D恰好在AF的垂直平分线上;
(3)点D、F在运动过程中是否存在t的值,使△DEF是直角三角形,若存在求出t的值,若不存在,说明理由.
(1)求证:四边形AEFD是平行四边形;
(2)当t为何值时,动点D恰好在AF的垂直平分线上;
(3)点D、F在运动过程中是否存在t的值,使△DEF是直角三角形,若存在求出t的值,若不存在,说明理由.
![](https://img.xkw.com/dksih/QBM/2021/9/11/2806017257963520/2810086432505856/STEM/221c1b3d-f79f-4cb0-9576-202573ec22c4.png)
更新时间:2021-09-17 15:18:23
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,
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(1)猜想并填空:
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【推荐1】如图,在
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(1)求证:四边形ABEF为菱形;
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【推荐2】如图,在四边形
中,
,
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的中点,连接
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