Question

mark the midpoint of $overline{ab}$.

Explanation:

Step1: Recall mid - point construction

The intersection of the perpendicular bisector of line segment $\overline{AB}$ and $\overline{AB}$ is the mid - point. Here, the lines $CD$ is the perpendicular bisector of $\overline{AB}$ (constructed by intersecting circles centered at $A$ and $B$ with equal radii greater than $\frac{1}{2}AB$).

Step2: Identify the mid - point

The point where $CD$ intersects $\overline{AB}$ is the mid - point of $\overline{AB}$.

Answer:

The intersection point of $CD$ and $\overline{AB}$ is the mid - point of $\overline{AB}$.