设椭圆C:
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024182835195598543/SYS201310241828351955985020_ST/0.png)
(a>b>0)的一个顶点坐标为A(
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024182835195598543/SYS201310241828351955985020_ST/1.png)
),且其右焦点到直线
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024182835195598543/SYS201310241828351955985020_ST/2.png)
的距离为3.
(1)求椭圆C的轨迹方程;
(2)若A、B是椭圆C上的不同两点,弦AB(不平行于y轴)的垂直平分线与x轴相交于点M,则称弦AB是点M的一条“相关弦”,如果点M的坐标为M(
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024182835195598543/SYS201310241828351955985020_ST/3.png)
),求证:点M的所有“相关弦”的中点在同一条直线上;
(3)对于问题(2),如果点M坐标为M(t,0),当t满足什么条件时,点M(t,0)存在无穷多条“相关弦”,并判断点M的所有“相关弦”的中点是否在同一条直线上.
考点分析:
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