7000÷7=____
402×3=____
15×2=____
Yesterday my father bought me ____ MP5. I like it very much.
已知sinα=-45,π<α<3π2,则cosα2的值为( )
已知样本容量是40,在样本的频数分布直方图中各小矩形的高之比依次为3:2:4:1,则第二小组的频数为____,第四小组的频率为____.