6. Let $O$ be a fixed point on a plane, and $A, B, C$ be three non-collinear points on the plane. A moving point $P$ satisfies
$$
\overrightarrow{O P}-\lambda \frac{\overrightarrow{A C}}{|\overrightarrow{A C}|}=\overrightarrow{O A}+\lambda \frac{\overrightarrow{A B}}{|\overrightarrow{A B}|}(\lambda \in[0,+\infty)) \text {. }
$$

Then the trajectory of point $P$ is . $\qquad$
6. The angle bisector of $\angle B A C$