A:13
B:14
C:34
D:12
(Ⅰ)求证:平面BCM⊥平面ACM.
(Ⅱ)若平面ABM⊥平面BCM,求三棱锥B﹣ACM外接球的直径.
The Shenzhou IX spacecraft returned to the earth safely _______ June 29th, 2012.
如图,转盘中8个扇形的面积都相等,任意转动转盘1次,当转盘停止转动时,指针指向大于6的数的概率为____.