I was looking for a birthday gift for my mother, but I couldn't find ______ suitable.
A:something
B:anything
C:nothing
D:everything
已知 , ,则tanα=____.
读图,回答下列各题。
如图所示,一波源在绳的左端发生半个波1,频率为f1,振幅为A1;同时另一波源在绳的右端发生半个波2,频率为f2,振幅为A2。图中AP=PB,由图可知( )
塔里木盆地主要的自然景观是( )