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如图,在矩形ABCD中,DE⊥AC于E,设∠ADE=α,且cosα=,AB=4,...
如图,在矩形ABCD中,DE⊥AC于E,设∠ADE=α,且cosα=
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,AB=4,则AD的长为( )
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095008_ST/images1.png)
A.3
B.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095008_ST/1.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095008_ST/2.png)
D.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095008_ST/3.png)
考点分析:
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如图,坡角为30°的斜坡上两树间的水平距离AC为2m,则两树间的坡面距离AB为( )
A.4m
B.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095007_ST/0.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095007_ST/1.png)
m
D.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095007_ST/2.png)
m
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△ABC中,若|cotA-1|+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095006_ST/0.png)
,则△ABC为( )
A.等腰三角形
B.直角三角形
C.等腰三角形或直角三角形
D.等腰直角三角形
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Rt△ABC中,∠C=90°,如果sinA=
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,那么cosB的值为( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095005_ST/1.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095005_ST/2.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095005_ST/3.png)
D.不能确定
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已知,直角坐标系中,点E(-4,2),F(-1,-1),以O为位似中心,按比例尺2:1把△EFO缩小,则点E的对应点E′的坐标为( )
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000455183609561/SYS201311030004551836095004_ST/images0.png)
A.(2,-1)或(-2,1)
B.(8,-4)或(-8,4)
C.(2,-1)
D.(8,-4)
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在Rt△ABC中,∠C=90°,CD⊥AB于D,下列等式中错误的是( )
A.AD•BD=CD
2B.AC•BD=CB•AD
C.AC
2=AD•AB
D.AB
2=AC
2+BC
2
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