请针对上传的第六题进行中文视频讲解。---**Question Number:** 6 **Question Stem:** As shown in the graph, a beam of light shoots from point $O$, reaches point $D$ which is on the mirror made up by line $A(1,0), B(0,1)$, is reflected by $AB$, then reaches the mirror made up by the $y$-axis, is reflected by the $y$-axis, then goes through point $A$. The coordinates of point $D$ are ______. **Points and Coordinates Mentioned:** Point $O$: Origin (implied by the graph) Point $A$: (1, 0) Point $B$: (0, 1) Point $D$: on line segment $AB$ **Chart Description:** - **Type:** 2D Cartesian Coordinate System graph. - **Main Elements:** - **Coordinate Axes:** Horizontal X-axis labeled 'x' with an arrow indicating the positive direction to the right. Vertical Y-axis labeled 'y' with an arrow indicating the positive direction upwards. The origin is labeled 'O' at the intersection of the axes. - **Points:** - Point O is at the origin (0,0). - Point A is labeled on the positive x-axis, approximately at a distance from O. The problem statement gives its coordinates as (1,0). - Point B is labeled on the positive y-axis, approximately at a distance from O. The problem statement gives its coordinates as (0,1). - **Lines:** - A straight line segment connects point A and point B. This line segment AB is described as a mirror. - The y-axis is also described as a mirror. **Other Relevant Text:** - The path of the beam of light is described as: $O \to D \text{ (on } AB) \to \text{ point on y-axis } \to A$. - Reflections occur at line $AB$ and the $y$-axis.