(选做题)请考生在A、B、C三题中任选一题作答,如果多做,则按所做的第一题记分.作答时请写清题号.
A.选修4-1(几何证明选讲)已知AD为圆O的直径,直线BA与圆O相切与点A,直线OB与弦AC垂直并相交于点G,与弧AC相交于M,连接DC,AB=10,AC=12.
(Ⅰ)求证:BA•DC=GC•AD;(Ⅱ)求BM.
B.选修4-4(坐标系与参数方程)求直线
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225403914470973/SYS201311012254039144709025_ST/0.png)
(t为参数)被曲线
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225403914470973/SYS201311012254039144709025_ST/1.png)
所截的弦长.
C.选修4-5(不等式选讲)(Ⅰ)求函数
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225403914470973/SYS201311012254039144709025_ST/2.png)
的最大值;
(Ⅱ)已知a≠b,求证:a
4+6a
2b
2+b
4>4ab(a
2+b
2).
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