How are you?
A:Fine, Thanks.
B:OK.
已知|AB|=2,动点P满足|PA|=2|PB|,试建立恰当的直角坐标系,动点P的轨迹方程为____.
选出句子中出现的单词( )
(Ⅰ)求证:BE⊥平面AD′C;
(Ⅱ)求平面D′AB与平面D′CE的所夹的锐二面角的大小.