A perpendicular bisector is a line that cuts AB in two equal parts, then the steps to follow are:
1. With a setting greather than 1/2 AB, place the compass point at A. Draw arcs above and below AB.
2. With the same setting, place the compass point at B. Draw arcs above and below AB
3. Label the points of intersection of the arcs E and F
4. Use a straightedge to draw EF