题目内容
(2010•龙岩)如图是圆心角为30°,半径分别是1、3、5、7、…的扇形组成的图形,阴影部分的面积依次记为S1、S2、S3、…,则S50= (结果保留π).![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232906294893484/SYS201310212329062948934016_ST/images0.png)
【答案】分析:由图可知S1=
,S2=
×3,S3=
×5,S4=
×7,…Sn=
×(2n-1),从而得出S50的值.
解答:解:由题意可得出通项公式:Sn=
×(2n-1),
即Sn=
×(2n-1),
∴S50=
π(100-1)=66π,
故答案为:66π.
点评:本题是一道规律性的题目,考查了扇形面积的计算,难度较大.
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232906294893484/SYS201310212329062948934016_DA/0.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232906294893484/SYS201310212329062948934016_DA/1.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232906294893484/SYS201310212329062948934016_DA/2.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232906294893484/SYS201310212329062948934016_DA/3.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232906294893484/SYS201310212329062948934016_DA/4.png)
解答:解:由题意可得出通项公式:Sn=
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232906294893484/SYS201310212329062948934016_DA/5.png)
即Sn=
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232906294893484/SYS201310212329062948934016_DA/6.png)
∴S50=
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131021232906294893484/SYS201310212329062948934016_DA/7.png)
故答案为:66π.
点评:本题是一道规律性的题目,考查了扇形面积的计算,难度较大.
![](http://thumb2018.1010pic.com/images/loading.gif)
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