A:take u
B:take o
C:take place
D:take off
在正三棱柱ABC﹣A1B1C1中,AB=2,AA1=3,点D为BC的中点;
(Ⅰ)求证:A1B∥平面AC1D;
(Ⅱ)若点E为A1C上的点,且满足 A1E→ =m EC→ (m∈R),若二面角E﹣AD﹣C的余弦值为 1010 ,求实数m的值.
——Where do you often exercise?——I often exercise in a park. It's close to my house.