See Section 27.5.2 for perpendicular bisectors in space.
The perpen_bisector command finds the perpendicular bisector of a line segment.
segment(1,i,color=blue); perpen_bisector(1,i) |
or:
S:=segment(1,i,color=blue); perpen_bisector(S) |
The perpen_bisector command can also take two lines as segments, in which case it returns and draws the perpendicular bisector of the segment from the first point defining the first line and the second point defining the second line.