由点P（1,-2）向圆x^2+y^2-6x-2y+6=0引得切线方程是

设切线方程y+2=k(x-1)y=kx-k-2kx-y-k-2=0x^2+y^2-6x-2y+6=0(x-3)^2+(y-1)^2=4圆心（3,1）半径2圆心到切线的距离=22=|3k-1-k-2|/根（k^2+1）k=5/12切线方程是y=5(x-1)/12-2显然x=1也是切线