KöMaL 2007 B4030

$AB$ is a given line segment in the plane. Consider all arbitrary points $C$ for which the triangle ABC is not isosceles. The exterior angle bisector of angle $C$ intersects the line $AB$ at $D$, and its intersection with the tangent drawn at point $A$ to the circle ADC is $P$. Determine the locus of all possible points $P$.