选做题
A.选修4-1:几何证明选讲
如图,自⊙O外一点P作⊙O的切线PC和割线PBA,点C为切点,割线PBA交⊙O于A,B两点,点O在AB上.作CD⊥AB,垂足为点D.
求证:
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024190840168098316/SYS201310241908401680983020_ST/0.png)
.
B.选修4-2:矩阵与变换
设a,b∈R,若矩阵
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024190840168098316/SYS201310241908401680983020_ST/1.png)
把直线l:y=2x-4变换为直线l′:y=x-12,求a,b的值.
C.选修4-4:坐标系与参数方程
求椭圆C:
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024190840168098316/SYS201310241908401680983020_ST/2.png)
=1上的点P到直线l:3x+4y+18=0的距离的最小值.
D.选修4-5不等式选讲
已知非负实数x,y,z满足x
2+y
2+z
2+x+2y+3z=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024190840168098316/SYS201310241908401680983020_ST/3.png)
,求x+y+z的最大值.
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