【简答题】序列 x(n) = cos (3 π n) 的周期等于()
【单选题】No sooner _____ the news than they rushed out into the street.
【单选题】已知4点序列x(n)=cos(πn),n=0,1,2,3,该序列的4点DFT为X(k),则X(0)=( )
【单选题】(Paragraph 2) The whole nation was shocked by the news the next day, and psychologists had no answers to explain why these people didn’t help.
A.
Only people in New York heard about the murder.
B.
News about the murder traveled quickly.
C.
The murder was not shocking to psychologists.
【判断题】类地行星包括水星、金星、地球和火星。()
【判断题】序列x(n) = sin(3πn/4) + cos(0.5πn)是周期序列。
【单选题】序列x(n)=cos(3 π n/8)的周期是( )。