explain how to construct a perpendicular bisector
http://www.mathsisfun.com/geometry/construct-linebisect.html
To construct a perpendicular bisector, you can follow these steps:
Step 1: Gather materials
You will need a compass, a ruler, and a pencil.
Step 2: Draw the line segment
Use the ruler to draw the line segment that you want to find the perpendicular bisector of. Make sure the line segment is long enough to accommodate the construction.
Step 3: Set the compass width
Adjust the width of the compass to a length greater than half of the line segment. This will ensure that the compass is wide enough to draw arcs.
Step 4: Place the compass at one end of the line segment
Place the tip of the compass at one end of the line segment and draw an arc that intersects the line segment.
Step 5: Place the compass at the other end of the line segment
Keeping the compass width the same, place the tip of the compass at the other end of the line segment and draw another arc that intersects the line segment. The two arcs should intersect each other.
Step 6: Draw a straight line
With the compass width still set, draw a straight line connecting the two intersection points of the arcs.
Step 7: Extend the line segment
Extend the line segment beyond its endpoints, using the ruler.
Step 8: Draw arcs
Place the compass at each endpoint of the line segment and draw arcs that intersect each other above and below the line segment.
Step 9: Draw a perpendicular bisector line
Using the ruler, draw a straight line connecting the intersections of the arcs. This line will be the perpendicular bisector of the original line segment.
Congratulations! You have successfully constructed a perpendicular bisector.