如图,已知过点D(0,-2)作抛物线C
1:
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=2py(p>0)的切线
l,切点A在第二象限.
(Ⅰ)求点A的纵坐标;
(Ⅱ)若离心率为
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的椭圆
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(a>b>0)恰好经过点A,设直线
l交椭圆的另一点为B,记直线
l,OA,OB的斜率分别为k,k
1,k
2,若k
1+2k
2=4k,求椭圆方程.
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解:(Ⅰ)由
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设切点
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,且
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,由切线
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的斜率为
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,得
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的方程为
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,又点
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在
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上,
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,即点

的纵坐标
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..........4分
(Ⅱ)由(Ⅰ)得
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,切线斜率

,
设
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,切线方程为
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,由
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,得
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,
所以椭圆方程为
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,且过

,
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……6分
由
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,
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, ........8分


……….10分
将
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,
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代入得:
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,所以
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,
椭圆方程为
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. ……….12分
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
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
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
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
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
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
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
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
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
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
,

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
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
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
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
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
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
.
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
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(Ⅱ)若直线

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
交于

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
两点,当

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
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

的右焦点为

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
与

轴交于点
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,若
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(其中

为坐标原点).
(Ⅰ)求椭圆


的方程;
(Ⅱ)设

是椭圆

上的任意一点,

为圆

的任意一条直径(

,

为直径的两个端点),求

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设椭圆

的左、右焦点分别为

、

,

是椭圆上的一点,

,原点

到直线

的距离为

,则椭圆的离心率为( )
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已知椭圆

中心在原点,焦点在坐标轴上,直线

与椭圆

在第一象限内的交点是
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,点
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在
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轴上的射影恰好是椭圆

的右焦点

,椭圆

另一个焦点是

,且
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(1)求椭圆

的方程;
(2)直线
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过点
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,且与椭圆
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交于
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两点,求
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的内切圆面积的最大值
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