如图,在平行六面体ABCD﹣A1B1C1D1中,若AB→=a→,AD→=b→,AA1→=c→,则D1B→=( )
例:
扁 偏(偏僻) 篇(篇章)
合 ____(____) ____(____)
昔 ____(____) ____(____)
一个扇形的半径为60cm,圆心角为120°,用它做一个圆锥的侧面,则圆锥的底面半径为( )
_____the difficulties in talking, they can understand each other by body language.( )