You need ______ warm clothes, or you' ll catch a cold.
A:to wearing
B:wears
C:to wear
D:wearing
已知a,b,c分别△ABC三个内角A,B,C所对的边,若AB→AB→+AC→AC→·BC→=0且△ABC的面积S△ABC=a2+c2-b24,则三角形△ABC的形状是( )
已知0<α<π2<β<π,tanα2=12,cosα-β=210
求sinα的值;
在国民经济中居于主体地位的是国有经济。( )