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如图1是一张Rt△ABC纸片,如果用两张相同的这种纸片恰好能拼成一个正三角形,如...
如图1是一张Rt△ABC纸片,如果用两张相同的这种纸片恰好能拼成一个正三角形,如图2,那么在Rt△ABC中,sin∠B的值是( )
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827006_ST/images0.png)
A.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827006_ST/0.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827006_ST/1.png)
C.1
D.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827006_ST/2.png)
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10名同学分成甲、乙两队进行篮球比赛,它们的身高(单位:cm)如下表所示:
| 队员1 | 队员2 | 队员3 | 队员4 | 队员5 |
甲队 | 177 | 176 | 175 | 172 | 175 |
乙队 | 170 | 175 | 173 | 174 | 183 |
设两队队员身高的平均数依次为
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,
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,身高的方差依次为S
甲2,S
乙2,则下列关系中完全正确的是( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827005_ST/2.png)
=
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,S
甲2>S
乙2B.
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=
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,S
甲2<S
乙2C.
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>
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,S
甲2>S
乙2D.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827005_ST/8.png)
<
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,S
甲2>S
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如图是由正方体和圆锥组成的几何体,它的俯视图是( )
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827004_ST/images0.png)
A.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827004_ST/images1.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827004_ST/images2.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827004_ST/images3.png)
D.
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下列事件是不可能事件的是( )
A.掷一次质地均匀的正方体骰子,向上的一面是4点
B.经过城市中某一有交通信号灯的路口,遇到绿灯
C.通常加热到100℃时,水沸腾
D.在只装有红球和绿球的袋子中摸出一个球,结果是黄球
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下列计算正确的是( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164346518582711/SYS201310221643465185827002_ST/0.png)
B.a+a
2=a
3C.(2a)•(3a)=6a
D.
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今年5月,我市第六次人口普查办公室发布了全市常住人口为578.99万人,用科学记数法可表示(保留2个有效数字)为( )
A.58×10
5人
B.5.8×10
5人
C.5.8×10
6人
D.0.58×10
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