In the triangle ABC, B (- 3,0). C (3,0). If the inscribed circle is x ^ 2 + y ^ 2-4x-2ky + 4 = 0, then the trajectory of vertex A is

In the triangle ABC, B (- 3,0). C (3,0). If the inscribed circle is x ^ 2 + y ^ 2-4x-2ky + 4 = 0, then the trajectory of vertex A is

From the known, the inscribed circle can be transformed into (X-2) ^ 2 + (Y-K) ^ 2 = k ^ 2, that is, the circle must pass through the point (2, K). If the center coordinate of the circle is O (2, K), then the slope of OB line is K1 = K / 4. If the vertex is a, then according to the inscribed circle in the known condition, so the angle ABC is bisected by the line ob, then the slope of OA can be calculated by double angle tangent