已知∠α=48°21′，则∠α的余角等于______．
∵∠α=48°21′，
∴∠α的余角等于90°-48°21′=41°39′．
故答案为41°39′．
The film ____ the old man of the days which he had spent sailing on the sea. [ ]
A. remembered
B. remained
C. reminded
D. returned
模拟乘法器的应用很广泛，但是不能用于（）电路。
A.振幅调制
B.调幅波的解调
C.频率调制
D.混频
