A:踏板对人的摩擦力可能为0
B:踏板支持力对人做的功大于人重力势能增量
C:踏板对人做的功等于人的机械能的增量
D:不计一切损耗,电梯消耗的电能等于人增加的机械能
函数y=cos2x﹣sinx的值域是( )
—I will have an important test tomorrow. I feel stressed now.—__________ and believe youself. You will pass it.
80-6=____
23-4=____
- Who's that old man? ( )
- He's my ________