A:2π4
B:2π2
C:2π
D:2 2π
如图,沿Rt△ABC的中位线DE剪切一刀后,用得到的△ADE和四边形DBCE拼图,下列图形:①平行四边形;②菱形;③矩形;④等腰梯形.一定能拼出的是( )
— I saw Helen in the school just now.
— It ______ be Helen. She has gone to the shopping center with her sister.
已知sin(π﹣α)=﹣23,且α∈(﹣π2,0),则tan(2π﹣α)=____