Question

已知圆C x^2+y^2+2x-4y+1=0 问从圆外一点P（x0,y0）向圆引切线PM,M为切点,O为原点,

Answer 1

圆C方程：（x+1）^2+(y-2)^2=2,所以圆心C（-1,2）,R^2=2设P点的坐标为（x,y）则｜PM｜^2=|PC|^2-R^2=（x+1）^2+(y-2)^2-R^2=x^2+y^2+2x-4y+3|PO|^2=x^2+y^2因为｜PM┃=┃PO┃,所以x^2+y^2+2x-4y+3=x^2+y^2,得点P的轨...