Test and analysis: (1) The straight line l 1 passes through the fixed point A (- 1, 0), so we can establish the point inclination equation of the straight line, and then calculate the value of k according to the tangent of the straight line and the circle. The distance from the center of the circle to the straight line is equal to the radius, but we should pay attention to discussing the situation that the slope does not exist first to avoid missing the solution.
(2) If the radius of circle D is 4, the center of circle D is on line L2: 2x+y-2 = 0, and it is inscribed with circle C, let the center of circle D be (a, 2-2a). Then, according to the inscribed circle, the distance between the center of the circle is equal to the absolute value of the radius difference, and the equation about A can be constructed, and the answer can be obtained by solving the equation.
Problem analysis: (1)① If the slope of the straight line does not exist, the straight line: meets the meaning of the question. 2 points
② If the slope of a straight line exists, let it exist.
4 points according to the meaning of the question.
Solution, ∴ straight line:. 7 points
The equation of the straight line is 0. 8 points.
(2) According to the meaning of the question,
From the meaning of the question, the center of the circle c, the radius of the center of the circle c, 12 point
Solution,
Or ... 14 point
∴ What is the equation of the circle? Or ... ? 16 point