【多选题】下列各项中,属于电子货币特征的是( )。
【多选题】下列各项中,属于电子货币的特征的是:( )
【简答题】&8226;Look at the graphs below. They show the imports and exports of eight different countries ( A - H) over the same three-year period. &8226;Which graph does each sentence (11 -15) describe? &8226;F...
【简答题】判断下列信号是否为周期信号,若是,确定其周期。 (1)f1(t) = sin2t + cos3t (2)f2(t) = cos2t + sinπt