题目内容
本题设有(1)、(2)、(3)三个选考题,每题7分,请考生任选2题作答,满分14分,如果多做,则按所做的前两题计分,作答时,先用2B铅笔在答题卡上把所选题目对应的题号涂黑,并将所选题号填入括号中.(1)选修4-2:矩阵与变换
设矩阵
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_ST/0.png)
(I)若a=2,b=3,求矩阵M的逆矩阵M-1;
(II)若曲线C:x2+y2=1在矩阵M所对应的线性变换作用下得到曲线C’:
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_ST/1.png)
(2)(本小题满分7分)选修4-4:坐标系与参数方程
在直接坐标系xOy中,直线l的方程为x-y+4=0,曲线C的参数方程为
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_ST/2.png)
(I)已知在极坐标(与直角坐标系xOy取相同的长度单位,且以原点O为极点,以x轴正半轴为极轴)中,点P的极坐标为(4,
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_ST/3.png)
(II)设点Q是曲线C上的一个动点,求它到直线l的距离的最小值.
(3)(本小题满分7分)选修4-5:不等式选讲
设不等式|2x-1|<1的解集为M.
(I)求集合M;
(II)若a,b∈M,试比较ab+1与a+b的大小.
【答案】分析:(1):(I)直接根据求逆矩阵的公式求解,即M=
,则
代入a,b即可求解
(II)设出曲线C:x2+y2=1任意一点为(x,y)经矩阵M所对应的线性变换作用下得到的点为(x,y),即可根据矩阵乘法M(x,y)=(x,y)得到关于x,y与x,y间的关系,即
将之代入
得到的含x,y的方程应与x2+y2=1相同,根据待定系数即可运算
(2):(I)将P的极坐标(4,
)根据公式
化为直角坐标坐标为(0,4),则根据直角坐标系下点与直线的位置关系判断即可
(II)根据曲线C的参数方程为
,设出曲线C上任一点到直线l的距离为d,则根据点到直线的距离公式知d=
,即d=
,而2sin(
)∈[-2,2],则d的最小值为![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/10.png)
(3):(I)直接根据绝对值不等式的意义((|a-b|表示a-b与原点的距离,也表示a与b之间的距离)知:-1<2x-1<1即可求解
(II)要比较ab+1与a+b的大小,只需比较(ab+1)-(a+b)与0的大小,而(ab+1)-(a+b)=(a-1)(b-1)再根据a,b∈M即可得到(a-1)(b-1)的符号,即可求解.
解答:(1)解:(I)∵![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/11.png)
∴![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/12.png)
将a=2,b=3代入即得:![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/13.png)
(II)设出曲线C:x2+y2=1任意一点为(x,y)经矩阵M所对应的线性变换作用下得到的点为(x,y),
∵M(x,y)=(x,y)
∴![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/14.png)
将之代入
得:![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/16.png)
即![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/17.png)
∵a>0,b>0
∴![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/18.png)
(2)(I)解∵P的极坐标为(4,
),![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/20.png)
∴P的直角坐标为(0,4)
∵直线l的方程为x-y+4=0
∴(0,4)在直线l上
(II)∵曲线C的参数方程为
,直线l的方程为x-y+4=0
设曲线C的到直线l的距离为d
则d=
=![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/23.png)
∵2sin(
)∈[-2,2]
∴d的最小值为![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/25.png)
(3)(I)解:∵|2x-1|<1
∴-1<2x-1<1
即0<x<1
即M为{x|0<x<1}
(II∵a,b∈M
∴a-1<0.b-1<0
∴(b-1)(a-1)>0
∴(ab+1)-(a+b)=a(b-1)+(1-b)=(b-1)(a-1)>0
即(ab+1)>(a+b)
点评:本题考查了逆变换与逆矩阵,以及待定系数法求解a,b的方法,椭圆的参数方程,绝对值不等式的解法,作差法比较大小的相关知识,属于基础题.
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/0.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/1.png)
(II)设出曲线C:x2+y2=1任意一点为(x,y)经矩阵M所对应的线性变换作用下得到的点为(x,y),即可根据矩阵乘法M(x,y)=(x,y)得到关于x,y与x,y间的关系,即
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/2.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/3.png)
(2):(I)将P的极坐标(4,
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/4.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/5.png)
(II)根据曲线C的参数方程为
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/6.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/7.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/8.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/9.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/10.png)
(3):(I)直接根据绝对值不等式的意义((|a-b|表示a-b与原点的距离,也表示a与b之间的距离)知:-1<2x-1<1即可求解
(II)要比较ab+1与a+b的大小,只需比较(ab+1)-(a+b)与0的大小,而(ab+1)-(a+b)=(a-1)(b-1)再根据a,b∈M即可得到(a-1)(b-1)的符号,即可求解.
解答:(1)解:(I)∵
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/11.png)
∴
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/12.png)
将a=2,b=3代入即得:
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/13.png)
(II)设出曲线C:x2+y2=1任意一点为(x,y)经矩阵M所对应的线性变换作用下得到的点为(x,y),
∵M(x,y)=(x,y)
∴
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/14.png)
将之代入
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/15.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/16.png)
即
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/17.png)
∵a>0,b>0
∴
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/18.png)
(2)(I)解∵P的极坐标为(4,
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/19.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/20.png)
∴P的直角坐标为(0,4)
∵直线l的方程为x-y+4=0
∴(0,4)在直线l上
(II)∵曲线C的参数方程为
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/21.png)
设曲线C的到直线l的距离为d
则d=
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/22.png)
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/23.png)
∵2sin(
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/24.png)
∴d的最小值为
![](http://thumb.1010pic.com/pic6/res/gzsx/web/STSource/20131023214328944832387/SYS201310232143289448323020_DA/25.png)
(3)(I)解:∵|2x-1|<1
∴-1<2x-1<1
即0<x<1
即M为{x|0<x<1}
(II∵a,b∈M
∴a-1<0.b-1<0
∴(b-1)(a-1)>0
∴(ab+1)-(a+b)=a(b-1)+(1-b)=(b-1)(a-1)>0
即(ab+1)>(a+b)
点评:本题考查了逆变换与逆矩阵,以及待定系数法求解a,b的方法,椭圆的参数方程,绝对值不等式的解法,作差法比较大小的相关知识,属于基础题.
![](http://thumb2018.1010pic.com/images/loading.gif)
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