A:a﹣3<b﹣3
B:3﹣a<3﹣b
C:ac>bc
D:a2>b2
如图,已知平面ADC∥平面A1B1C1,B为线段AD的中点,△ABC≈△A1B1C1,四边形ABB1A1为正方形,平面AA1C1C丄平面ADB1A1,A1C1=A1A,∠C1A1A= π3 ,M为棱A1C1的中点.
(I)若N为线段DC1上的点,且直线MN∥平面ADB1A1,试确定点N的位置;
(Ⅱ)求平面MAD与平面CC1D所成的锐二面角的余弦值.
读世界某海区洋流分布示意图(图),完成下列各题.
—But now they just _______ and wait for you to offer them pet food.