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(2008上海高考,5)若向量,满足||=1,| |=2,且与的夹角为,则|+|=______________.
将椭圆绕其左焦点逆时针方向旋转90°后所得椭圆方程是
A.2 B.4 C.8 D.16
A.8 B.12 C.9 D.16