(2008•资阳)先化简,再求值:
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131021230847578060836/SYS201310212308475780608029_ST/0.png)
,其中x=1.
考点分析:
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(2006•厦门)对于直角坐标平面内的任意两点A(x
1,y
1),B(x
2,y
2),定义它们之间的一种“距离”:
||AB||=|x
2-x
1|+|y
2-y
1|.给出下列三个命题:
①若点C在线段AB上,则||AC||+||CB||=||AB||;
②在△ABC中,若∠C=90°,则||AC||
2+||CB||
2=||AB||
2;
③在△ABC中,||AC||+||CB||>||AB||.其中真命题的个数为( )
A.0
B.1
C.2
D.3
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某同学用牙膏纸盒制作一个如图所示的笔筒,笔筒的筒底为长4.5厘米,宽3.4厘米的矩形.则该笔筒最多能放半径为0.4厘米的圆柱形铅笔( )
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A.20支
B.21支
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如图,在锐角△ABC中,以BC为直径的半圆O分别交AB,AC与D、E两点,且
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,则S
△ADE:S
四边形DBCE的值为( )
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A.
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B.
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C.
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D.
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运算与推理以下是甲、乙两人得到
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+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131021230847578060836/SYS201310212308475780608025_ST/1.png)
>
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的推理过程:(甲)因为
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131021230847578060836/SYS201310212308475780608025_ST/3.png)
>
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131021230847578060836/SYS201310212308475780608025_ST/4.png)
=3,
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>
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=2,所以
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+
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>3+2=5.又
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=
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<
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=5,所以
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+
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>
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.(乙)作一个直角三角形,两直角边长分别为
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,
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.利用勾股定理得斜边长的平方为14长,所以
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+
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>
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.对于两个人的推理,下列说法中正确的是( )
A.两人都正确
B.两人都错误
C.甲正确,乙错误
D.甲错误,乙正确
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(2008•呼和浩特)图(1),(2),(3),(4)四个几何体的三视图为以下四组平面图形,其中与图(3)对应的三视图是( )
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A.
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B.
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C.
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D.
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