770. It is required to divide the segment $\boldsymbol{A} \boldsymbol{B}$ in half. How should the radii of the arcs described from points $\boldsymbol{A}$ and $\boldsymbol{B}$, as centers, be chosen so that the construction is as accurate as possible?
770. The arcs must intersect at a right angle; for this, the radii must be equal to $\frac{A B \sqrt{2}}{2}$ or, by eye, slightly less than $\frac{3}{4} \boldsymbol{A} \boldsymbol{B}$.