题目内容
(2005•甘肃)如图,在△ABC,∠B=30°,sin c=![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232116259421977/SYS201310212321162594219007_ST/0.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232116259421977/SYS201310212321162594219007_ST/images1.png)
【答案】分析:如图,作AD⊥BC于点D,在直角三角形ADB和ADC利用锐角三角函数的概念解决问题.
解答:
解:如图,过A作AD⊥BC于点D,
在Rt△ADC中,AD=ACsinC=10×
=8,
在Rt△ADB中,AB=
=
=16,
∴AB=16.
点评:本题通过作辅助线,在一般三角形中构造直角三角形,再利用锐角三角函数的概念来求解.
解答:
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232116259421977/SYS201310212321162594219007_DA/images0.png)
在Rt△ADC中,AD=ACsinC=10×
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232116259421977/SYS201310212321162594219007_DA/0.png)
在Rt△ADB中,AB=
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232116259421977/SYS201310212321162594219007_DA/1.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232116259421977/SYS201310212321162594219007_DA/2.png)
∴AB=16.
点评:本题通过作辅助线,在一般三角形中构造直角三角形,再利用锐角三角函数的概念来求解.
![](http://thumb2018.1010pic.com/images/loading.gif)
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