Final answer:
To construct a perpendicular bisector of a segment HK, place the compass at the endpoints H or K and draw arcs with a radius greater than half of HK's length. The perpendicular bisector is the line connecting the intersection points of these arcs.
Step-by-step explanation:
To construct the perpendicular bisector of a line segment HK, you need to place the point of the compass at either endpoint of the segment (H or K) and draw an arc that intersects the line above and below it. The radius of the arc should be more than half the length of the line segment to ensure the arcs intersect when drawn from both endpoints. The intersection points of the arcs, when connected, give you the line that is the perpendicular bisector of HK. This line will be equidistant from the endpoints H and K and will intersect HK at a 90-degree angle.
If HK is 12 units long, then the radius of your arcs should be more than 6 units to ensure that the arcs intersect. Assuming the length of HK is known, the compass radius should be set to any length greater than half of HK's length but less than the full length (for practicality and ease of drawing), such as 9 units, if we follow the provided example.
Remember, accurate construction involves careful measurements with the compass and straightedge (or ruler), and the process can be repeated to increase precision.