直线l：2xsinα+2ycosα+1=0，圆C：x2+y2+2xsinα+2ycosα=0，l与C的位置关系是（ ）
A．相交
B．相切
C．相离
D．不能确定
圆C：x2+y2+2xsinα+2ycosα=0 即 （x+sinα）2+（y+cosα）2=1，
表示以C（-sinα-cosα）为圆心，半径等于1的圆．
圆心到直线的距离为d=
=1=r，故直线和圆相切，|-2sin2α-2cos2α| 4sin2α+4cos2α
故选：B．
| 阅读下面的对话，根据上下文，从所给的七个句子中选择五个句子，将对话补充完整。 | |
Chen Jie: I went to the hospital yesterday. Zhang Peng: ____________________? Chen Jie: Yes, I was sick. Zhang Peng: ____________________? Chen Jie: I had a headache, I got the flu. Zhang Peng: You should do sports and make yourself to be stronger. Chen Jie: You are right. ____________________? ZhangPeng: Good idea. But I will play basketball this afternoon. Chen Jie: ____________________? ZhangPeng: Sure! Let's go together. |