题目内容
在同圆或等圆中,如果![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/0.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/1.png)
(1)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/2.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/3.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/4.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/5.png)
(3)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/6.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/7.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/8.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_ST/9.png)
A.1个
B.2个
C.3个
D.4个
【答案】分析:由在同圆或等圆中,
的长度=
的长度,根据弧长公式得到它们所对的圆心角相等,再根据在同圆或等圆中,如果两个圆心角以及它们对应的两条弧、两条弦中有一组量相等,则另外两组量也对应相等,即可对选项进行判断.
解答:解:∵在同圆或等圆中,
的长度=
的长度,
∴弧AB和弧CD所对的圆心角相等,
∴
的度数等于
的度数;
∴
和
是等弧;
∴
所对的弦的弦心距等于
所对的弦的弦心距.
故选D.
点评:本题考查了在同圆或等圆中,如果两个圆心角以及它们对应的两条弧、两条弦中有一组量相等,则另外两组量也对应相等.在圆中经常利用此结论把圆心角、弧、弦之间进行转化.
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/0.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/1.png)
解答:解:∵在同圆或等圆中,
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/2.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/3.png)
∴弧AB和弧CD所对的圆心角相等,
∴
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/4.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/5.png)
∴
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/6.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/7.png)
∴
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/8.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201222505823290/SYS201311032012225058232001_DA/9.png)
故选D.
点评:本题考查了在同圆或等圆中,如果两个圆心角以及它们对应的两条弧、两条弦中有一组量相等,则另外两组量也对应相等.在圆中经常利用此结论把圆心角、弧、弦之间进行转化.
![](http://thumb2018.1010pic.com/images/loading.gif)
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