(1)设P(x,y),由椭圆定义可知,点P的轨迹C是以(0,- 3 ),(0, 3 )为焦点,长半轴为2的椭圆.它的短半轴b= 22?( 3 )2 =1,故曲线C的方程为x2+ y2 4 =1.(2)①设过点(0, 3 )的直线方程为y=kx+ 3 ,A(x1,y1),B(x2,y2),其坐标满足