如图1,已知在Rt△ABC中,AB=5cm,BC=12cm,以BC为边作正方形BCDE,点P从点A出发,沿ABE方向匀速运动,速度为1cm/s;同时,点Q从点C出发,沿CA方向匀速运动,速度为2cm/s,连接PQ.设运动时间为t(s)(0<t<6.5),解答下列问题:
(1)当t为何值时,PQ∥BC?
(2)如图2,连接PQ,交BC于点F,是否存在某一时刻t,使△BFP与△QFC相似?
(3)用含t的代数式表示出五边形PEDCQ的面积.
(1)当t为何值时,PQ∥BC?
(2)如图2,连接PQ,交BC于点F,是否存在某一时刻t,使△BFP与△QFC相似?
(3)用含t的代数式表示出五边形PEDCQ的面积.
![](https://img.xkw.com/dksih/QBM/2021/11/12/2849477860745216/2853445661835264/STEM/d070b48c-e385-4c52-83a8-eff1883fcd44.png)
更新时间:2021-11-17 21:32:58
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【推荐1】【问题提出】:比较代数式a与b的大小.
【问题探究】:要比较代数式a与b的大小,只要求出它们的差
,若
,则
;若
,则
;若
,则
;,反之亦然.
【问题解决】:
(1)如图,有A、B两种型号的钢板,A型钢板的面积比B型钢板大,制作某产品有两种用料方案,方案1:用4块A型钢板,8块B型钢板;方案2:用3块A型钢板,9块B型钢板.从省料角度考虑,应选哪种方案?请说明理由;
米,宽为b米,B菜地的长为
米,宽为
米,试比较两块长方形菜地周长的大小;
(3)如图,正方形
的边长为a,以A为圆心,
为半径作圆弧.以D为圆心,a为半径作圆弧.若图中阴影部分的面积分别为
、
,请你比较
与
的大小.
【问题探究】:要比较代数式a与b的大小,只要求出它们的差
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c9f2416d1f75a45a314331146550832e.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c6a46e678bf9d2df5ad4c782b3dc22f5.png)
【问题解决】:
(1)如图,有A、B两种型号的钢板,A型钢板的面积比B型钢板大,制作某产品有两种用料方案,方案1:用4块A型钢板,8块B型钢板;方案2:用3块A型钢板,9块B型钢板.从省料角度考虑,应选哪种方案?请说明理由;
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d8653ad77169d73f8983262ced1b0ed6.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/51653e4140c6c44ab1f9ca69dd97453c.png)
(3)如图,正方形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
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【推荐2】甲、乙两家商场以同样的价格出售同样的电器,但各自推出的优惠方案不同,甲商场规定:凡超过
元的电器,超出的金额按
收取;乙商场规定:凡超过
元的电器,超出的金额按
收取,某顾客购买的电器价格是
元.
(1)当
时,分别用代数式表示在两家商场购买电器所需付的费用
(2)当
时,该顾客应选择哪一家商场购买比较合算?说明理由.
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(1)当
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(2)当
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【推荐1】如图,△ABC中,∠B=∠C=75°,BC=2,P、Q分别是AB、AC边上的两个动点,满足∠BPQ=75°,求线段PB的取值范围.
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【推荐2】把一张长方形的纸片
沿对角线
折叠,折叠后,边
的对应边
交
于F.
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(1)求证:
;
(2)若
,
.求点F至
的距离.
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(1)求证:
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(2)若
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【推荐1】如图,在
中,
,
,
,动点P从点B出发,沿折线B→A→C路线,以5cm/s的速度匀速运动到点C停止,动点 Q从点C出发,沿折线C→B→A路线,以4cm/s的速度匀速运动到点A停止.点P,点Q同时出发,运动时间为t秒,以PQ为直径作⊙O:
![](https://img.xkw.com/dksih/QBM/2021/11/6/2845526006800384/2846099628343296/STEM/5a5e98fd-488e-4e6c-8781-21d336a53bee.png)
(1)当点P在边AB上运动,点Q在边CB上运动时,⊙O与BC相切,求t的值;
(2)当⊙O与AB相切时,求t的值.
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(1)当点P在边AB上运动,点Q在边CB上运动时,⊙O与BC相切,求t的值;
(2)当⊙O与AB相切时,求t的值.
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【推荐2】如图,DC是⊙O的直径,点B在圆上,直线AB交CD延长线于点A,且∠ABD=∠C.
(1)求证:AB是⊙O的切线;
(2)若AB=4cm,AD=2cm,求CD的长.
(1)求证:AB是⊙O的切线;
(2)若AB=4cm,AD=2cm,求CD的长.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/4/17/80d79708-37ac-4a2b-b0ae-3bc287e4cd60.png?resizew=222)
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