enterno
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共回答了23个问题采纳率:91.3% 举报
(1)设l的解析式为y=kx+b,
把A(8,0)、B(0,
![](https://img.yulucn.com/upload/6/b2/6b264fd6b8477b3d3538561e0b9edd94_thumb.jpg)
)分别代入解析式得,
![](https://img.yulucn.com/upload/e/28/e2863a53ecae7ae822ff606828200942_thumb.jpg)
,
解得k=-
![](https://img.yulucn.com/upload/5/12/512164cb5aa438281e0f856d18579c74_thumb.jpg)
,
则函数解析式为y=-
![](https://img.yulucn.com/upload/3/af/3afc21f57a51a9919f9a4d7880d4bc79_thumb.jpg)
x+8
![](https://img.yulucn.com/upload/c/21/c21b52dbdce8e183a3a0daca78d60bf7_thumb.jpg)
,
将y=-
![](https://img.yulucn.com/upload/5/50/5508374a9f043fcf72c93783d656bf3a_thumb.jpg)
x+8
![](https://img.yulucn.com/upload/9/da/9da0acf11c089551ecae2b739114e08b_thumb.jpg)
和y=
![](https://img.yulucn.com/upload/3/85/385b2e225adc75a5994cd7040a97be41_thumb.jpg)
x组成方程组得,
![](https://img.yulucn.com/upload/6/1f/61fe3a617c56580a9dd4c8d1d60147c8_thumb.jpg)
,
解得
![](https://img.yulucn.com/upload/3/3a/33a9c729ffaad284da2f9ab17e047eb2_thumb.jpg)
,
故得C(4,
![](https://img.yulucn.com/upload/b/dd/bddd98aed604cbee92bc142873455f2b_thumb.jpg)
),
∵OA=8,
∴t的取值范围是:0≤t≤4;
(2)作EM⊥y轴于M,DG⊥y轴于点G,
∵D点的坐标是(t,
![](https://img.yulucn.com/upload/2/76/276799a64d1c101c75f5b8a4af1f8ada_thumb.jpg)
),E的坐标是(t,
![](https://img.yulucn.com/upload/f/2f/f2f64bbd43582180897c7d21839527aa_thumb.jpg)
)
∴DE=
![](https://img.yulucn.com/upload/b/27/b276f366abc78cf929a28770e2d2d509_thumb.jpg)
-
![](https://img.yulucn.com/upload/b/1c/b1cc2e41225f2cfaa59416329c96db49_thumb.jpg)
=
![](https://img.yulucn.com/upload/a/02/a0206ff82c33eeec4fbde47e6659cd00_thumb.jpg)
;
∴等边△DEF的DE边上的高为:
![](https://img.yulucn.com/upload/1/74/174c147d90e3953c548ba99a59d881d1_thumb.jpg)
DE=12-3t;
根据E点的坐标,以及∠MNE=60°,
得出MN=
![](https://img.yulucn.com/upload/6/5d/65d6395ba8ab2f94ae4623c71b42bbf1_thumb.jpg)
t,
同理可得:GH=
![](https://img.yulucn.com/upload/1/45/145115880675d3acbb304a7fc3cb5542_thumb.jpg)
t,
∴可求梯形上底为:
![](https://img.yulucn.com/upload/d/65/d6555a5241e3bfbcae30fc77fc05908a_thumb.jpg)
-
![](https://img.yulucn.com/upload/1/ee/1eee228117a3f9ffad8010091455286f_thumb.jpg)
,
∴当点F在BO边上时:12-3t=t,
∴t=3;
当0≤t<3时,重叠部分为等腰梯形,可求梯形面积为:
S=
![](https://img.yulucn.com/upload/6/da/6dac30597f5173889d6530dd89ae22c9_thumb.jpg)
=
![](https://img.yulucn.com/upload/c/4a/c4a78e4332cff5c7bd05597e04fd79e8_thumb.jpg)
=
![](https://img.yulucn.com/upload/a/3e/a3e3b48707142da118e35f635aa4a782_thumb.jpg)
;
当3≤t≤4时,重叠部分为等边三角形
S=
=
![](https://img.yulucn.com/upload/d/3d/d3de396e2c05bc8d3f1144b3556131cb_thumb.jpg)
;
(3)存在,P(
![](https://img.yulucn.com/upload/2/fc/2fcd0825b3fa202f0bf8a2f352bca032_thumb.jpg)
,0);
说明:∵FO≥
![](https://img.yulucn.com/upload/a/1b/a1bd9b168240b2252a3d6222ad487258_thumb.jpg)
,FP≥
![](https://img.yulucn.com/upload/f/7e/f7e03afab029d93b154e343f92474eef_thumb.jpg)
,OP≤4,
∴以P,O,F以顶点的等腰三角形,腰只有可能是FO,FP,
若FO=FP时,t=2(12-3t),t=
![](https://img.yulucn.com/upload/9/39/939c9b791d64226af3b95bf1888b36af_thumb.jpg)
,
∴P(
![](https://img.yulucn.com/upload/6/2d/62d91dd0bcdfbff81bab096cc3955898_thumb.jpg)
,0)。
1年前
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