函数y=cos2x-sin2x的周期是______．
函数y=cos2x-sin2x=cos2x
∵ω=2
∴T=2π÷2=π
故答案为：π．
Jack is good, hard-working and intelligent. _____, I can’t speak too highly of him.
A．As a result
B．In a word
C．In other words
D．Above all
在货物进出境过程中，有时还需办理“报检、报验”手续，一般而言，报检、报验手续要先于报关手续办理。( )
