题目

已知向量a=（sinB，1-cosB）与向量b=（2，0）的夹角为，其中A、B、C是△ABC的内角. （1）求B的大小；（2）求sinA+sinC的取值范围. 答案：解：(1)∵A与B的夹角为， ∴=cos=.                                                                                              又∵===cos，                                                 且0＜＜,∴=,则B=.               I have been studying computer for several years and I still ________． [　　] A．have B．do C．have been D．am