题目
题型:不详难度:来源:
求证
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-64954.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-79524.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-58193.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-25037.png)
∵ BC∥GF,
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-64954.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-33116.png)
又 ∠BDC=90°,BE=EC,
∴ BE=DE.
∵ BE∥GF,
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235344-44873.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235344-84950.png)
∴ DF=GF.
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-64954.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-79524.png)
方法二:作EH∥AB交AC于点H.
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-64954.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235344-48786.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-79524.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235344-75983.png)
∠BDC=90°,BE=EC,
∴ BE=DE.
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-64954.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235343-79524.png)
解析
核心考点
举一反三
求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235338-28572.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235338-80409.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235339-94599.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235334-68669.png)
小题1:DG2=BG·CG;
小题2:BG·CG=GF·GH.
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235330-43202.png)
小题1:当BD与a、b之间满足怎样的关系时,△ABC∽△CDB?
小题2:过A作BD的垂线,与DB的延长线交于点E,若△ABC∽△CDB.
求证四边形AEDC为矩形(自己完成图形).
发,以每秒2 cm的速度沿CA、AB运动到点B,则从C点出发多少秒时,可使
S△BCP=
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235324-54129.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235324-77950.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235308-66639.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235308-77689.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235308-28153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235309-77926.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235309-64201.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235309-76513.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235309-41557.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235309-77926.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235309-98294.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235310-47287.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235310-19460.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235310-12474.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235310-49781.png)
小题1:试比较
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235310-22702.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235311-57659.png)
小题2:令
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235311-65026.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235311-74835.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235311-74835.png)
小题3:在(2)的条件下,若
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235311-64492.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235308-77689.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235311-22788.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235311-93464.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235312-24745.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235312-59065.png)
小题4:在(3)的条件下,若抛物线
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235312-86626.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235312-29785.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235312-60227.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235309-77926.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235312-76087.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235312-60227.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235313-10693.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235312-76087.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235313-49223.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235313-58026.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235313-33309.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235313-64642.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235313-83150.png)
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