--How do you think I can make up with Tom? --Put aside ____you disagree and try to find ______you have in common. A. what; what B. what; where C. where; what D. what; whether 答案:C如图1,在Rt△ABC中,∠C=90°,BC=3,AC=6,D,E分别是AC,AB上的点,且DE∥BC,DE=2,将△ADE沿DE折起到△A1DE的位置,使A1C⊥CD,如图2.
(I)求证:A1C⊥平面BCDE;
(II)若M是A1D的中点,求CM与平面A1BE所成角的大小;