19.解:(Ⅰ)(法一)将圆方程化为标准方程 ······ 1分 ∴ 圆C的圆心,半径······················ 2分 圆心到直线:的距离 ···················· 5分 因此直线与圆相交.·························· 6分 (法二)将直线化为, 由 得 ∴直线过定点···························· 3分 点在圆内,····························· 5分 ∴直线与圆相交 ···························· 6分 (法三)联立方程消去并整理得, 3分 恒成立 ············· 5分 ∴直线与圆相交 ···························· 6分 (Ⅱ)设圆心到直线的距离为, 则,··················· 9分 又,∴ ,解得:,··········· 11分 ∴ 所求直线为或.················ 12分 |