To bisect an angle, use this table:
Given angle ABC, use a compass to draw an arc at any convenient
radius from the apex.
Using the compass set at slightly more than half the distance from
A to C and with the compass points at the intersections of the arc
and angle legs (E and F), draw two short arcs that intersect at D.
Draw a straight line from A to D. This bisector divides the original
given angle into two equal angles.
Figure 2-19 shows how to bisect an angle.
Figure 2-19.Bisecting angles.