函数y=2cos2x的值域是______．
∵-1≤cosx≤1
∴0≤cos2x≤1∴0≤y≤2
故答案为：[0，2]
The agency helps people find childcare, including putting families in touch with baysitters for______.
A．employ
B．sale
C．repair
D．hire
当闻及胸壁伤口处有气体出入的声音时是以下哪种损伤
A．多处肋骨骨折
B．闭合性气胸
C．开放性气胸
D．张力性气胸
E．损伤性血胸
