题目内容
已知△ABC的三边长分别为![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_ST/0.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_ST/1.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_ST/2.png)
A.
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_ST/3.png)
B.
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_ST/4.png)
C.
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_ST/5.png)
D.
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_ST/6.png)
【答案】分析:根据题中数据先计算出两相似三角形的相似比,则第三边长可求.
解答:解:根据题意,易证△ABC∽△A′B′C′,且相似比为:
:1,
∴△A′B′C′的第三边长应该是
=
.
故选A.
点评:本题考查了相似三角形的性质:相似三角形的对应边成比例.
解答:解:根据题意,易证△ABC∽△A′B′C′,且相似比为:
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_DA/0.png)
∴△A′B′C′的第三边长应该是
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_DA/1.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103101323612830615/SYS201311031013236128306004_DA/2.png)
故选A.
点评:本题考查了相似三角形的性质:相似三角形的对应边成比例.
![](http://thumb2018.1010pic.com/images/loading.gif)
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