题目

若函数f(x)=-asincos(π-)的最大值为2，试确定常数a的值. 答案：解析：f(x)=+asincos=cosx+sinx=sin(x+φ)，其中角φ满足sinφ=.由已知有=4.解之，得a=±. Do you know the girl ________ father owns a company? [　　] A．who B．which C．that D．whose