x=0是垂直与x轴且与圆相切的直线设另一条不与x轴垂直的切线为y=kx+3圆心(2, 0)到切线的距离为半径2即2=|2k+3|/√(1+k²)4(1+k²)=(2k+3)²4=12k+9k=-5/12即另一条切线为y=-(5/12)x+3
